NB5 Daily Build 200511271900 with Mustang Build 61

I encounted the following while:
1) at java.awt.Frame line 540, right click at this.peer
2) "Goto" --> "Declaration"
3) java.awt.Component showed up and cursor is at the right place (line 174), 
but then IAE is thrown.

java.lang.IllegalArgumentException: Child tree not found (type: 41 firstToken: 
1059 lastToken: 1100 resource: javax/swing/JFrame.java) class 
org.netbeans.jmi.javamodel.Method$Impl isDefaultLookAndFeelDecorated 
valid:true | class org.netbeans.jmi.javamodel.JavaClass$Impl 
javax.swing.JFrame valid:true | class org.netbeans.jmi.javamodel.Resource$Impl 
javax/swing/JFrame.java valid:true | 
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.getASTree
(MetadataElement.java:1160)
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.getASTree
(MetadataElement.java:515)
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.cachePositions
(ResourceImpl.java:485)
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.cachePositions
(ResourceImpl.java:491)
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.ResourceImpl.getFeaturePosition
(ResourceImpl.java:473)
	at 
org.netbeans.modules.javacore.jmiimpl.javamodel.FeatureImpl.getPosition
(FeatureImpl.java:270)
	at org.netbeans.modules.javacore.JMManager.getElementPosition
(JMManager.java:725)
	at org.netbeans.modules.javacore.JMManager.getElementPosition
(JMManager.java:711)
	at org.netbeans.modules.java.OverrideAnnotation$Descriptor.getLine
(OverrideAnnotation.java:157)
	at org.netbeans.modules.java.OverrideAnnotation.updateLine
(OverrideAnnotation.java:64)
	at org.netbeans.modules.java.OverrideAnnotationSupport$1.run
(OverrideAnnotationSupport.java:149)
	at org.netbeans.editor.BaseDocument.render(BaseDocument.java:1126)
	at 
org.netbeans.modules.java.OverrideAnnotationSupport.processOverriddenAnnotation
(OverrideAnnotationSupport.java:156)
	at 
org.netbeans.modules.java.OverrideAnnotationSupport.processOverriddenAnnotation
Impl(OverrideAnnotationSupport.java:180)
	at org.netbeans.modules.java.OverrideAnnotationSupport.access$400
(OverrideAnnotationSupport.java:45)
	at 
org.netbeans.modules.java.OverrideAnnotationSupport$Request.computeAnnotations
(OverrideAnnotationSupport.java:362)
	at org.netbeans.modules.java.OverrideAnnotationSupport$Request.run
(OverrideAnnotationSupport.java:346)
	at org.openide.util.RequestProcessor$Task.run
(RequestProcessor.java:493)
[catch] at org.openide.util.RequestProcessor$Processor.run
(RequestProcessor.java:926)