I use my script all the time and suddenly it was 
not happy. Was idle for long time.

This is 3.6RC2, don't recall seeing it in RC1.

Not sure how repeatable.

java.lang.IllegalStateException: Error in 
org.apache.tools.ant.module.nodes.AntProjectChildr
en with entry Key ([property: null], 0) probably 
caused by faulty key implementation. The key 
hashCode() and equals() methods must behave as 
for an IMMUTABLE object and the hashCode() must 
return the same value for equals() keys.
	at org.openide.nodes.Children.updateOrder
(Children.java:781)
	at org.openide.nodes.Children.setEntries
(Children.java:672)
	at org.openide.nodes.Children$3.run
(Children.java:1878)
	at org.openide.util.Mutex.postRequest
(Mutex.java:867)
	at org.openide.util.Mutex.postWriteRequest
(Mutex.java:364)
	at 
org.openide.nodes.Children$Keys.applyKeys
(Children.java:1886)
	at org.openide.nodes.Children$Keys.setKeys
(Children.java:1845)
	at 
org.apache.tools.ant.module.nodes.ElementChildren.
refreshKeys(ElementChildren.java:102)
	at 
org.apache.tools.ant.module.nodes.AntProjectChildr
en.stateChanged(AntProjectChildren.java:79)
	at 
org.apache.tools.ant.module.xml.AntProjectSupport$
ChangeFirer.run(AntProjectSupport.java:568)
	at org.openide.util.Task.run
(Task.java:136)
	at 
org.openide.util.RequestProcessor$Task.run
(RequestProcessor.java:330)
[catch] at 
org.openide.util.RequestProcessor$Processor.run
(RequestProcessor.java:686)