Description of problem:
Closing Firefox with two or more open tabs and being prompted whether to really quit, cancel or save and quit causes system to believe, that Firefox is not responding and asks user to wait or Fill firefox.

Version-Release number of selected component (if applicable):
3.6.20

How reproducible:
Always 

Steps to Reproduce:
1. Open several tabs in Firefox
2. Close Firefox
3. When prompted whether to quit, cancel or save and quit wait a few seconds
  
Actual results:
System reports 'Firefox is not responding'

Expected results:
No warning -- Firefox is responding, just waiting for user input.

Additional info:
This is not exactly a problem with Firefox, it's probably issue with something else (also happens with seamonkey) -- so if someone knows where to file it...

It's definitely reproducible on ia64 and s390x.