Product Version = NetBeans IDE Dev (Build 201110100600)
Operating System = Windows XP version 5.1 running on x86
Java; VM; Vendor = 1.7.0
Runtime = Java HotSpot(TM) Client VM 21.0-b17
After working for a while, the source folder of the project tree became empty. Trying to navigate with Shift-Ctrl-1 selected the source folder but did not display any sub folder (packages displayed as tree).
In the files tree, all sources had been available. Only restart of NB helped to get a proper function again.
By now, I don't know how to reproduce this bug, it happened only once. I'll file messages.log.
Created attachment 111845 [details]
I am not sure what exactly can be your problem, but I see in the log a lot of warnings from java.project.support.ui.TreeRootNode$PackageFilterChildren.copyNode
The support seems to be querying node.getLookup().lookup(DataObject.class) directly in AWT which is ineffective. I guess first of all the java.project.support.ui.TreeRootNode$PackageFilterChildren.copyNode should be rewritten and then we can speculate why your folder is empty (if you will be able to reproduce the problem then).
Doing node.getLookup().lookup(DataObject.class) may be inefficient (even I don't know why as these nodes are DataNodes which take the DO in constructor) but it should not have any effect on the fact that the nodes are not visible.
The warnings from java.project.support.ui.TreeRootNode$PackageFilterChildren.copyNode is fixed,
Fixed jet-main 002c73ed1b13.
The rest has nothing in common with TreeNode and cannot be reproduced.