Strange errors on exit

[Thomas Dybdahl Ahle]

When I close my (gtk) program, I get errors like the below.
It seams that when the interpreter shuts down, it sets every variable to 
None, but continues running the threads, (seems only in cases where 
they've just been asleep)
I don't think this would be intended behavior?

Exception in thread Thread-4 (most likely raised during interpreter 
shutdown):
Traceback (most recent call last):
  File "/usr/lib/python2.4/threading.py", line 442, in __bootstrap
  File "/home/thomas/Programmering/python/skak/0.7/lib/pychess/System/
ThreadPool.py", line 49, in run
  File "/usr/lib/python2.4/Queue.py", line 89, in put
  File "/usr/lib/python2.4/threading.py", line 237, in notify
exceptions.TypeError: exceptions must be classes, instances, or strings 
(deprecated), not NoneType
Unhandled exception in thread started by 
Error in sys.excepthook:

Original exception was: