Errors running builder 'AspectJ Builder' on project

I am working on SpringSource Tool Suite with Spring Roo. Everything was working well up until few days ago after I installed GWT plugin (I think this might be a problem, I am not sure ).

Every time I code something and press Save (ctrl+s), it shows a dialog box showing

    Errors occurred during the build.
Errors running builder 'AspectJ Builder' on project xyz123
org/eclipse/ajdt/core/builder/AJBuilder$SourceFilesChangedVisitor


eclipse.buildId=2.6.0.201103161000-RELEASE
java.version=1.6.0_24
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_US
Framework arguments:  -product com.springsource.sts.ide
Command-line arguments:  -os win32 -ws win32 -arch x86_64 -product com.springsource.sts.ide


Error
Wed Apr 27 14:33:03 EDT 2011
Problems occurred when invoking code from plug-in: "org.eclipse.开发者_C百科core.resources".

java.lang.ClassFormatError: org/eclipse/ajdt/core/builder/AJBuilder$SourceFilesChangedVisitor
at org.eclipse.ajdt.core.builder.AJBuilder.sourceFilesChanged(AJBuilder.java:1707)
at org.eclipse.ajdt.core.builder.AJBuilder.hasChangesAndMark(AJBuilder.java:1639)
at org.eclipse.ajdt.core.builder.AJBuilder.build(AJBuilder.java:185)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:629)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:172)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:203)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:255)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:258)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:311)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:343)
at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:144)
at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:242)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)

Can anyone please help me out in solving this?

Thanks,

The ClassFormatError occurs when a class file is malformed or corrupted. See here:

http://download.oracle.com/javase/6/docs/api/java/lang/ClassFormatError.html

It could very well be that your installation of AJDT was somehow corrupted. I would recommend trying one or all of the following:

1. Uninstall the Google plugin. Does the problem go away?
2. Upgrade to the latest dev snapshot of AJDT. Update site is here: http://download.eclipse.org/tools/ajdt/36/dev/update After upgrading does your error go away?
3. As a last resort, try reinstalling STS. You can leave your workspace in tact, just unzip STS again.