1) I start up the program in debug mode (F5)
2) I do the actions in my app to reach the break point
3) NetBeans stops the execution at the set break point
4) Now I press (F8 Step over)
5) NetBeans "hangs" (100% CPU)
   I mean: 
6) I Alt+Tab to my app and back to NetBeans
7) It takes ages for NetBeans to paint its GUI
8) When at last it has becomes responsive again, I see that
9) it has opened the file ThreadLocal.java and the cursor 
   is on the first line of the get() method ????
10) I press the "Pause" button but nothing happens
11) I press "Step Over" again (although it wasn't stopped)
    (All step over, step out, step in buttons become disabled now)
12) I Alt+Tab back to my app (that 'builds up' very slowly - 100% CPU)
13) I cancel the dialog that came up by pressing a certain app button
14) I press that button again (to reach the breakpoint again)
15) I press (F8 Step over)
16) 100% CPU which drops after half a minute
17) I Alt+Tab to my app again: 100% CPU until it drops after half a minute
   And so on. Not workable.

I posted this on nbusers@netbeans.org and David Strupl answered:

> 5) NetBeans "hangs" (100% CPU)
> ...
> 16) 100% CPU which drops after half a minute
If you consistently get this behavior you should:

1. Start NB from command line (dos prompt on win platforms, make sure 
you have big enough window)
2. When you see 100% CPU do a thread dump, several times (!). Save them 
to a .txt file.
3. Create an issue for it, attach your thread dump file there

Well, here's the thread dump file. During the "hang" of NetBeans I was only 
able to create two thread dumps (they were also slowly created)