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Eclipse not responding on startup

For some reason this evening I can't launch my Eclipse anymore? I don't know what to take from these logs, as I am not that experienced with Eclipse. Any help will be highly appreciated! The log from Eclipses .log file when it freezes on startup to "not responding":
I don't know what to take from these logs, as I am not that experienced with Eclipse
!MESSAGE Warning: The environment variable HOME is not set. The following directory will be used to store the Git
user global configuration and to define the default location to store repositories: 'C:\Users\Calgary'. If this is
not correct please set the HOME environment variable and restart Eclipse. Otherwise Git for Windows and
EGit might behave differently since they see different configuration options.
This warning can be switched off on the Team > Git > Confirmations and Warnings preference page.
!ENTRY org.eclipse.lsp4e 4 0 2020-10-07 01:52:01.676
!MESSAGE
!STACK 0
java.util.concurrent.TimeoutException
at java.base/java.util.concurrent.CompletableFuture.timedGet(CompletableFuture.java:1957)
at java.base/java.util.concurrent.CompletableFuture.get(CompletableFuture.java:2092)
at org.eclipse.lsp4e.operations.declaration.OpenDeclarationHyperlinkDetector.detectHyperlinks(OpenDeclarationHyperlinkDetector.java:90)
at org.eclipse.ui.texteditor.HyperlinkDetectorRegistry$HyperlinkDetectorDelegate.detectHyperlinks(HyperlinkDetectorRegistry.java:81)
at org.eclipse.jface.text.hyperlink.HyperlinkManager.findHyperlinks(HyperlinkManager.java:289)
at org.eclipse.jface.text.hyperlink.HyperlinkManager.findHyperlinks(HyperlinkManager.java:262)
at org.eclipse.jface.text.hyperlink.HyperlinkManager.mouseMove(HyperlinkManager.java:457)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:216)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4105)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1037)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3922)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3524)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1160)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1049)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:658)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:557)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:154)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:150)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:137)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:107)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:657)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
at org.eclipse.equinox.launcher.Main.run(Main.java:1447)
!SESSION 2020-10-08 01:41:14.347 -----------------------------------------------
eclipse.buildId=4.15.0.I20200305-0155
java.version=13.0.2
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=fi_FI
Framework arguments: -product org.eclipse.epp.package.jee.product
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.jee.product```

That looks similar to issue 545447 affecting LSP4E, the project includes the necessary code to integrate any language server (conforming to the Language Server Protocol specification) or Debug Adapter (conforming to the Debug Adapter Protocol) in the Eclipse IDE.
It is supposed to be fixed with lsp4e 0.10.0.
Try and see if the issue persists when downloading (for testing) the latest Eclipse.
(Upgrade from your current 4.15.0.I20200305-0155 to a current Eclipse 4.17 2020-09)
Check also if there is any space in the paths involved by your Eclipse workspace.

I can not open Eclipse

I'm trying to open Eclipse with a workspace that I normally use, but I got an error. Here is a part from the log (Any help is really appreciated):
!SESSION 2014-01-22 10:01:39.699 -----------------------------------------------
eclipse.buildId=4.3.0.M20130911-1000
java.version=1.7.0_45
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_US
Framework arguments: -product org.eclipse.epp.package.standard.product
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.standard.product
This is a continuation of log file D:\PhD_SVN\Code\.metadata\.bak_0.log
Created Time: 2014-01-22 15:17:42.504
!ENTRY org.eclipse.ui 4 0 2014-01-22 15:17:42.507
!MESSAGE Unhandled event loop exception
!STACK 0
java.lang.reflect.UndeclaredThrowableException
at com.sun.proxy.$Proxy15.mouseMove(Unknown Source)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:212)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4170)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3759)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1113)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:997)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:138)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:610)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:567)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:354)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:181)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:636)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:591)
at org.eclipse.equinox.launcher.Main.run(Main.java:1450)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor63.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.eclipse.wb.internal.draw2d.EventManager$8.invoke(EventManager.java:325)
... 27 more
Caused by: java.lang.NullPointerException
at org.eclipse.wb.draw2d.Figure.getFigureCanvas(Figure.java:372)
at org.eclipse.wb.draw2d.Figure.getFigureCanvas(Figure.java:372)
at org.eclipse.wb.draw2d.FigureUtils.translateFigureToCanvas(FigureUtils.java:100)
at org.eclipse.wb.core.controls.palette.PaletteComposite.getTargetFigure(PaletteComposite.java:1167)
at org.eclipse.wb.core.controls.palette.PaletteComposite.access$6(PaletteComposite.java:1164)
at org.eclipse.wb.core.controls.palette.PaletteComposite$EntryFigure.move_showFeedback(PaletteComposite.java:831)
at org.eclipse.wb.core.controls.palette.PaletteComposite$EntryFigure.access$12(PaletteComposite.java:827)
at org.eclipse.wb.core.controls.palette.PaletteComposite$EntryFigure$2.mouseMove(PaletteComposite.java:793)
at org.eclipse.wb.internal.draw2d.EventManager$4.invokeListener(EventManager.java:267)
at org.eclipse.wb.internal.draw2d.EventManager.sendEvent(EventManager.java:205)
at org.eclipse.wb.internal.draw2d.EventManager.handleMouseEvent(EventManager.java:191)
at org.eclipse.wb.internal.draw2d.EventManager.mouseMove(EventManager.java:184)
... 31 more
!ENTRY org.eclipse.ui 4 0 2014-01-22 15:17:42.511
!MESSAGE Unhandled event loop exception
!STACK 0
For more information, my Eclipse has only one plugin which is a GUI plug-in to create GUI with simple drag and drop mechanism.. Furthermore, all my code inside the workspace is OSGI bundles

I don't know why you even need to install a plugin to get a drag and drop mechanism in Eclipse, but to quote IT Crowd:
Have you tried turning it off and on again? (Delete->Re-install)

The simplest solution is to backup your eclipse and adt folders when they're working nicely.
With this in mind, reinstall eclipse and back it up when it's running nicely.
Don't forget to give it as much memory as you can spare, especially if you're emulating an android device.

According to the FAQ at the eclipse wiki.
http://wiki.eclipse.org/FAQ_How_do_I_remove_a_plug-in%3F
There is no mechanism within Eclipse to permanently and physically
uninstall a feature and its plug-ins. The process to physically and
permanently remove an undesirable feature and its plug-ins is a manual
process that should be done when Eclipse is not running. In order to
do, you will have to manually remove the files there associated with
the feature from the eclipse/features directory and its plug-ins from
the eclipse/plugins directory. Be very cautious as to which files you
delete, and always have a backup of your Eclipse directory. If you
remove the wrong files from these directories, you may have quite some
trouble restoring your Eclipse to a stable state. Therefore, unless
your hard disk storage capacity is extraordinarily limited, it is
recommended that you simply leave the physical files in place.
If it does not work, you can always download eclipse again and reinstall all other plugins you got. If you don't remember with one you got you can check directory eclipse/plugins.
In the future you should have a backup of eclipse every time you deiced to install a new plugin that way you can just roll back if anything goes wrong.

java.lang.RuntimeException: Application "org.eclipse.ui.ide.workbench" could not be found in the registry

i am using Eclipse v21.10.1-569685 and JDK version 1.7.0_13-b20
When i downloaded new updates (Help-> Install New Software) after that Eclipse asked me to restart the software, but i faced with this error:
!SESSION 2013-04-10 06:49:45.348 -----------------------------------------------
eclipse.buildId=v21.1.0-569685
java.version=1.7.0_13
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_US
Framework arguments: -product com.android.ide.eclipse.adt.package.product
Command-line arguments: -os win32 -ws win32 -arch x86 -product com.android.ide.eclipse.adt.package.product
!ENTRY org.eclipse.osgi 2 0 2013-04-10 06:49:47.671
!MESSAGE One or more bundles are not resolved because the following root constraints are not resolved:
!SUBENTRY 1 org.eclipse.osgi 2 0 2013-04-10 06:49:47.671
!MESSAGE Bundle reference:file:plugins/org.eclipse.e4.ui.workbench.addons.swt_0.10.1.v20120827-151636.jar was not resolved.
!SUBENTRY 2 org.eclipse.e4.ui.workbench.addons.swt 2 0 2013-04-10 06:49:47.672
!MESSAGE Missing required bundle org.eclipse.e4.ui.model.workbench_0.9.1.
!SUBENTRY 1 org.eclipse.osgi 2 0 2013-04-10 06:49:47.672
.
.
.
.
!ENTRY org.eclipse.osgi 4 0 2013-04-10 06:49:47.941
!MESSAGE Application error
!STACK 1
java.lang.RuntimeException: Application "org.eclipse.ui.ide.workbench" could not be found in the registry. The applications available are: org.eclipse.equinox.app.error, org.eclipse.equinox.p2.director, org.eclipse.equinox.p2.garbagecollector.application, org.eclipse.equinox.p2.publisher.InstallPublisher, org.eclipse.equinox.p2.publisher.EclipseGenerator, org.eclipse.equinox.p2.publisher.ProductPublisher, org.eclipse.equinox.p2.publisher.FeaturesAndBundlesPublisher, org.eclipse.equinox.p2.reconciler.application, org.eclipse.equinox.p2.repository.repo2runnable, org.eclipse.equinox.p2.repository.metadataverifier, org.eclipse.equinox.p2.artifact.repository.mirrorApplication, org.eclipse.equinox.p2.metadata.repository.mirrorApplication, org.eclipse.equinox.p2.updatesite.UpdateSitePublisher, org.eclipse.equinox.p2.publisher.UpdateSitePublisher, org.eclipse.equinox.p2.publisher.CategoryPublisher, org.eclipse.update.core.standaloneUpdate, org.eclipse.update.core.siteOptimizer, org.eclipse.ant.core.antRunner, org.eclipse.cdt.codan.core.application, org.eclipse.cdt.core.GeneratePDOM, org.eclipse.help.base.infocenterApplication, org.eclipse.help.base.helpApplication, org.eclipse.help.base.indexTool, org.eclipse.jdt.apt.core.aptBuild, org.eclipse.jdt.core.JavaCodeFormatter, org.eclipse.jdt.core.JavaIndexer.
at org.eclipse.equinox.internal.app.EclipseAppContainer.startDefaultApp(EclipseAppContainer.java:248)
at org.eclipse.equinox.internal.app.MainApplicationLauncher.run(MainApplicationLauncher.java:29)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
What should i do to run the Eclipse?

OK thanks everyone I found the solution, which was the following:
Control Panel → View advanced system settings → Advanced tab → Environment Variables
Now you have to do 2 things:
Create a new variable (click the New button):
Variable name: JAVA_HOME
Variable value: C:\Program Files\Java\[your Java Version]
Edit the Path variable and add this to the end of that:
;%JAVA_HOME%\bin

DELETE (or just move to a temporary folder) your $home/.eclipse folder (i.e., the config folder).
It worked for me.

The "org.eclipse.ui.ide.workbench" application is included in the org.eclipse.platform plugin. This plugin isn't include in your instance because some reason. Maybe, installing ADT invalid it.
Try to restore old configuration (Help>About>Installation details>Installation History) and reinstall ADT again.

Maybe eclipse -clean will help? First delete plugin adt from Help->Install->What is already Installed, second install adt from Market place, use Eclipse for Java or C++ developers (this with the Java schema).

Eclipse: java.lang.RuntimeException: Application “org.eclipse.ui.ide.workbench” could not be found in the registry

Iam using helios eclipse (eclipse-SDK-3.6.1-win32).
I update this Helps > Check of updates
I have updated completely by checking all. (Most of them was plugin related to android)
After completion of updates, it asked me to restart eclipse. After that, when ever i start eclipse it shows error. It shows the following dialog
An error has occurred. See the log file
D:\eclipse-SDK-3.6.1-win32\eclipse\configuration\11003434.log.
That log is
!SESSION 2011-05-11 12:06:34.453 -----------------------------------------------
eclipse.buildId=M20110210-1200
java.version=1.6.0_24
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_US
Command-line arguments: -os win32 -ws win32 -arch x86
!ENTRY org.eclipse.osgi 2 0 2011-05-11 12:06:36.593
!MESSAGE One or more bundles are not resolved because the following root constraints are not resolved:
!SUBENTRY 1 org.eclipse.osgi 2 0 2011-05-11 12:06:36.593
!ENTRY org.eclipse.osgi 4 0 2011-05-11 12:06:36.687
!MESSAGE Application error
!STACK 1
java.lang.RuntimeException: Application "org.eclipse.ui.ide.workbench" could not be found in the registry. The applications available are: org.eclipse.equinox.app.error, org.eclipse.equinox.p2.director.app.application, org.eclipse.equinox.p2.director, org.eclipse.equinox.p2.garbagecollector.application, org.eclipse.equinox.p2.publisher.InstallPublisher, org.eclipse.equinox.p2.publisher.EclipseGenerator, org.eclipse.equinox.p2.publisher.ProductPublisher, org.eclipse.equinox.p2.publisher.FeaturesAndBundlesPublisher, org.eclipse.equinox.p2.repository.repo2runnable, org.eclipse.equinox.p2.repository.metadataverifier, org.eclipse.equinox.p2.artifact.repository.mirrorApplication, org.eclipse.equinox.p2.metadata.repository.mirrorApplication, org.eclipse.equinox.p2.updatesite.UpdateSitePublisher, org.eclipse.equinox.p2.publisher.UpdateSitePublisher, org.eclipse.equinox.p2.publisher.CategoryPublisher, org.eclipse.pde.junit.runtime.uitestapplication, org.eclipse.pde.junit.runtime.legacytestapplication, org.eclipse.pde.junit.runtime.coretestapplication, org.eclipse.pde.junit.runtime.coretestapplicationnonmain, org.eclipse.pde.junit.runtime.nonuithreadtestapplication, org.eclipse.update.core.standaloneUpdate, org.eclipse.update.core.siteOptimizer, org.eclipse.ant.core.antRunner, org.eclipse.equinox.p2.metadata.generator.EclipseGenerator, org.eclipse.equinox.p2.reconciler.application, org.eclipse.help.base.infocenterApplication, org.eclipse.help.base.helpApplication, org.eclipse.help.base.indexTool, org.eclipse.jdt.apt.core.aptBuild, org.eclipse.jdt.core.JavaCodeFormatter, org.eclipse.pde.build.Build.
at org.eclipse.equinox.internal.app.EclipseAppContainer.startDefaultApp(EclipseAppContainer.java:248)
at org.eclipse.equinox.internal.app.MainApplicationLauncher.run(MainApplicationLauncher.java:29)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:620)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:575)
at org.eclipse.equinox.launcher.Main.run(Main.java:1408)
I didn't understand anything.
Can anyone help me in this.
I'm really stuck

Did you try running eclipse.exe -clean?
Any cached data used by the OSGi
framework and eclipse runtime will be
wiped clean. This will clean the
caches used to store bundle dependency
resolution and eclipse extension
registry data. Using this option will
force eclipse to reinitialize these
caches.

its clearly saying that some dependcies plugins were not been installed, so please reslove the dependency .
Better you post the same in Eclipse forum, they will provide you solution.

Eclipse 3.5 customized with some plugins fails to start on target machine

i have been creating a customized Eclipse Version with some specific Plugins (CDT, AVR-Development) and after configuring and testing successfully on my machine, I zipped the eclipse-Folder and send it to my client to install onto the target machine.
But when he tries to start eclipse he gets the following error in the Logfile:
!SESSION 2010-06-28 19:24:57.856 -----------------------------------------------eclipse.buildId=unknown
java.version=1.6.0_20
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=de_DE
Framework arguments: -product org.eclipse.epp.package.cpp.product
Command-line arguments: -os win32 -ws win32 -arch x86 -product org.eclipse.epp.package.cpp.product
!ENTRY org.eclipse.osgi 4 0 2010-06-28 19:24:58.870
!MESSAGE Bundle reference:file:org.eclipse.equinox.simpleconfigurator_1.0.101.R35x_v20090807-1100.jar#1:start not found.
!ENTRY org.eclipse.osgi 4 0 2010-06-28 19:24:58.886
!MESSAGE Application error
!STACK 1
java.lang.IllegalStateException: Unable to acquire application service. Ensure that the org.eclipse.core.runtime bundle is resolved and started (see config.ini).
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:74)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
This looks like some files are missing or the configuration is wrong, but i can't reproduce the error. I removed my workspace, moved the eclipse Folder around, tried everything under another User-Account.
Does anyone have an Idea why this works on my machine (it was a vanilla Win7-Installation) but fails on his (also, Win7 - fresh install) ?
FYI, here's the configuration file, works on my machine:
#This configuration file was written by: org.eclipse.equinox.internal.frameworkadmin.equinox.EquinoxFwConfigFileParser
#Thu Jun 10 14:10:03 CEST 2010
org.eclipse.update.reconcile=false
eclipse.p2.profile=epp.package.cpp
osgi.instance.area.default=#user.home/workspace
osgi.framework=file\:plugins/org.eclipse.osgi_3.5.2.R35x_v20100126.jar
osgi.bundles=reference\:file\:org.eclipse.equinox.simpleconfigurator_1.0.101.R35x_v20090807-1100.jar#1\:start
org.eclipse.equinox.simpleconfigurator.configUrl=file\:org.eclipse.equinox.simpleconfigurator/bundles.info
eclipse.product=org.eclipse.platform.ide
osgi.splashPath=platform\:/base/plugins/org.eclipse.platform
osgi.framework.extensions=
osgi.bundles.defaultStartLevel=4
eclipse.p2.data.area=#config.dir/../p2/
eclipse.application=org.eclipse.ui.ide.workbench
Any help is highly appreciated, thanks! :)

Are you using a .product to produce your custom Eclipse build? Or are you adding plugins to an existing Eclipse build?
Either way, I'd recommend uzipping exactly what you sent your customer on a different machine than your development box. It may give you a better chance to reproduce the problem.
Based on the traces, this product "org.eclipse.epp.package.cpp.product" is in use. My guess is that the plugin that defines the Application referenced by that product is either missing from your zip, or one of its dependencies is missing.
If you add -console and -noExit as command line arguments, you can get to the OSGi prompt. You can then type 'ss' to see the status of all the bundles. If you then type 'start ' for any resolved bundles you can see why they didn't start. This sort of debugging can be helpful when you are out of other ideas.
Using the 'ss' command on your system that is working and the system that is not will help identify if you are missing any bundles or have bundles in different states.