Created attachment 36132 [details]
89644_thread dump

It's often reproducible if you open nb with clear userdir and try to create new
appl with new jframe or jpanel
I am increasing priority because nowadays it's more common.

I guess you will have to attach message.log next time you see problem like 
this. As the code in CloneableEditorSupport:

throw new InterruptedException("Waiting 10s for AWT and nothing! Exiting to 
prevent deadlock"); // NOI18N

try {
  safe.waitForResult();
} catch (InterruptedException ex) {
  ERR.log(Level.INFO, null, ex);
  return false;
}

is likely good enough to prevent this kind of deadlock. Please attach the 
messages.log, the exception should be there.

now this issue doesn't happen (Build 070820)