In Eclipse Helios it is impossible to rollback plugin installation

I have eclipse Helios for Java EE and I downloaded all the pluggins related to Modeling Framework. After this all the Java EE aspects are lost! Anyway it is not possible to uninstall the plugins or revert to previous installation.

If I select a plugin and press uninstall I get:

An error occurred while uninstalling session context was:(profile=e开发者_C百科pp.package.jee, phase=org.eclipse.equinox.internal.p2.engine.phases.Uninstall, operand=[R]org.eclipse.acceleo.common.source 3.0.1.v201009150438 --> null, action=org.eclipse.equinox.internal.p2.touchpoint.eclipse.actions.RemoveSourceBundleAction). org/eclipse/equinox/internal/simpleconfigurator/utils/SimpleConfiguratorUtils org/eclipse/equinox/internal/simpleconfigurator/utils/SimpleConfiguratorUtils

If I select yesterday's installation and press revert I get:

An error occurred while uninstalling session context was:(profile=epp.package.jee, phase=org.eclipse.equinox.internal.p2.engine.phases.Uninstall, operand=[R]com.google.collect 0.8.0.v201008251220 --> null, action=org.eclipse.equinox.internal.p2.touchpoint.eclipse.actions.UninstallBundleAction). org/eclipse/equinox/internal/simpleconfigurator/utils/SimpleConfiguratorUtils org/eclipse/equinox/internal/simpleconfigurator/utils/SimpleConfiguratorUtils

Why can't I unistall plugins? Is this some issue in Helios??

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I assume you followed :

Help => About Eclipse => Installation Detail => Installed Software Tab => and then selected a product to remove - from the exception that was Acceleo => Uninstall....

And that this yielded the error log you quote.

So I'd consider a 'manual' uninstall.

I've downloaded the acceleo v3 update site and looked into both the plugins and feature folders and all artifacts are named org.eclipse.acceleo.stuff. This is confirmed by looking into the content.xml (content.jar)

So, I'd backup my eclipse folder, remove all acceleo plugins and features, have a look in my workspace .metadata folder for corresponding memos (the acceleo name again as a filter) and restart with eclipse -clean.

That should start up again. Otherwse, goto restore !

As for the google collection bundle. It looks like there was another intervening installation (best interpretation I could come up with, I'm afraid ;-) because I can't see the google collections jar in the acceleo update site.

Update
In light of the investigation carried out (see comments below), I'd advise a fresh installation starting with the newer stable 3.6sr1 (Java EE variant) and progressively re-installing the existing plugins (as listed in Help => About Eclipse => Installation Detail => Installed Software) one by one from their respective update sites (export from preferences from old installation, reimport in new). The make new installation point on "old" workspace. Then look at the log view (or log in .metadata) to find out whether all plugins re-installed correctly).