FULL PRODUCT VERSION :
java version "1.6.0_10-beta"
Java(TM) SE Runtime Environment (build 1.6.0_10-beta-b22)
Java HotSpot(TM) Client VM (build 11.0-b11, mixed mode, sharing)

FULL OS VERSION :
Linux localhost.localdomain 2.6.20.1 #3 SMP Sun Mar 25 22:45:33 CEST 2007 i686 i686 i386 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
When running proguard-4.2 to process some of my jars I constantly get a java.lang.IncompatibleClassChangeError and my build-process aborts.

The strange thing is this only happens when running with -client, when running with -server everything works fine.
Also running proguard with java-5 everything works as expected.

However I don't know wether this error only happens with my jar-files, so if you whish I could send you a small package containing a jar-file and the approproate configuration-file to trigger the problem. Don't hestitate to mail me ;)
By the way there were other reports about this problem at the proguard-forums already.


THE PROBLEM WAS REPRODUCIBLE WITH -Xint FLAG: No

THE PROBLEM WAS REPRODUCIBLE WITH -server FLAG: No

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1.) Run proguard-4.2 on JDK6u10 and let it shrink some jar
2.) proguard will abort with the exception

EXPECTED VERSUS ACTUAL BEHAVIOR :
no errors
ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" java.lang.IncompatibleClassChangeError
        at proguard.classfile.attribute.LineNumberTableAttribute.accept(LineNumberTableAttribute.java:70)
        at proguard.classfile.attribute.CodeAttribute.attributesAccept(CodeAttribute.java:173)
        at proguard.classfile.util.ClassReferenceInitializer.visitCodeAttribute(ClassReferenceInitializer.java:277)
        at proguard.classfile.attribute.CodeAttribute.accept(CodeAttribute.java:75)
        at proguard.classfile.ProgramMethod.attributesAccept(ProgramMethod.java:62)
        at proguard.classfile.util.ClassReferenceInitializer.visitProgramMethod(ClassReferenceInitializer.java:128)
        at proguard.classfile.ProgramMethod.accept(ProgramMethod.java:54)
        at proguard.classfile.ProgramClass.methodsAccept(ProgramClass.java:388)
        at proguard.classfile.util.ClassReferenceInitializer.visitProgramClass(ClassReferenceInitializer.java:95)
        at proguard.classfile.ProgramClass.accept(ProgramClass.java:281)
        at proguard.classfile.ClassPool.classesAccept(ClassPool.java:114)
        at proguard.Initializer.execute(Initializer.java:97)
        at proguard.ProGuard.initialize(ProGuard.java:210)
        at proguard.ProGuard.execute(ProGuard.java:85)
        at proguard.ProGuard.main(ProGuard.java:499)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
I can send a self-contained test-case by email.
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CUSTOMER SUBMITTED WORKAROUND :
build with JDK5

Release Regression From : 6u6
The above release value was the last known release where this 
bug was not reproducible. Since then there has been a regression.