I have managed to repeat this problem on a version of NetBeans 6.0 beta 2
To get NetBeans working again, I removed all files starting org-dHb-*
NetBeans then restarted ok (I don't think this is an official fix
Have identified the problem and produced a new version which works with NetBeans 5.5 and 6.0 beta 2, available as before.
Sorry for the inconvenience and hope you try the new vesion.