Hi. This looks to be similar to issue #63732, but the error trace is different, so I'm submitting it.

java version "1.5.0_05"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_05-83)
Java HotSpot(TM) Client VM (build 1.5.0_05-48, mixed mode, sharing)

NetBeans IDE 5.0 (Build 200601251500)
Mac OS X version 10.4.5 running on ppc

It happened when (I think after a compilation) I've seen a red "do not enter" like icon in bottom right 
corner of Netbeans. So I've clicked at it, and it showed up the error details (below). I will attach a 
messages.log file if there is a facility to do it.

Thank you.

A java.lang.IllegalStateException exception has occurred.
Please report this at http://www.netbeans.org/community/issues.html,
including a copy of your messages.log file as an attachment.
The messages.log file is located in your /Users/peterk/.netbeans/5.0/var/log folder.

java.lang.IllegalStateException: Recursive call to getElementInfo()
	at org.netbeans.modules.javacore.jmiimpl.javamodel.SemiPersistentElement.getElementInfo
(SemiPersistentElement.java:201)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.initChildren(ResourceImpl.java:
322)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.initChildren(ResourceImpl.java:
316)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.initCheck
(MetadataElement.java:140)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.SemiPersistentElement.checkUpToDate
(SemiPersistentElement.java:269)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.SemiPersistentElement.checkUpToDate
(SemiPersistentElement.java:267)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.JavaClassImpl.getTypeParameters
(JavaClassImpl.java:423)
	at org.netbeans.jmi.javamodel.JavaClass$Impl.getTypeParameters(Unknown Source)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ParameterizedTypeImpl.initSubstitutionMap
(ParameterizedTypeImpl.java:318)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ParameterizedTypeImpl.getInnerClass
(ParameterizedTypeImpl.java:200)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.resolveType
(MetadataElement.java:1547)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.resolveType
(MetadataElement.java:1540)
	at org.netbeans.modules.javacore.parser.MDRParser.resolveClass(MDRParser.java:969)
	at org.netbeans.modules.javacore.parser.MDRParser.resolveSuperTypes(MDRParser.java:1192)
	at org.netbeans.modules.javacore.parser.MDRParser.processAST(MDRParser.java:402)
	at org.netbeans.modules.javacore.parser.MDRParser.processAST(MDRParser.java:491)
	at org.netbeans.modules.javacore.parser.MDRParser.processAST(MDRParser.java:373)
	at org.netbeans.modules.javacore.parser.MDRParser.processAST(MDRParser.java:335)
	at org.netbeans.modules.javacore.parser.MDRParser.processAST(MDRParser.java:313)
	at org.netbeans.modules.javacore.parser.MDRParser.enterMembers(MDRParser.java:243)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.directUpdate
(ResourceImpl.java:733)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.checkUpToDate
(ResourceImpl.java:644)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.checkUpToDate
(ResourceImpl.java:587)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.initResource
(ResourceImpl.java:430)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.initCheck
(MetadataElement.java:134)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.SemiPersistentElement.getElementInfo
(SemiPersistentElement.java:185)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.initChildren(ResourceImpl.java:
322)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.initChildren(ResourceImpl.java:
316)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.initCheck
(MetadataElement.java:140)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.SemiPersistentElement.checkUpToDate
(SemiPersistentElement.java:269)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.JavaClassImpl.getContents
(JavaClassImpl.java:411)
	at org.netbeans.jmi.javamodel.JavaClass$Impl.getContents(Unknown Source)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.findMainIn(ResourceImpl.java:
1705)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.getMain(ResourceImpl.java:
1691)
	at org.netbeans.modules.java.JavaNode.hasMain(JavaNode.java:632)
	at org.netbeans.modules.java.JavaNode.resolveIcons(JavaNode.java:592)
	at org.netbeans.modules.java.JavaNode$StateUpdater.updateNodes(JavaNode.java:709)
	at org.netbeans.modules.java.JavaNode$StateUpdater.run(JavaNode.java:702)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:493)
[catch] at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:926)