eloff: It may be that there are different problems that all show the symptom; *this* problem reported here can only occur if you are using multiple threads (atleast for the ValueError; haven't looked into the crash at all).

Yes, you can run multiple threads, and yes, you can use logging freely. However, you should not let the main thread just "run off". Instead, you should end your main thread with an explicit .join() operation on all threads it has created; those threads themselves should perform explicit .join() operations on all threads they create. That way, you can guarantee orderly shutdown. threading.py tries to do the joining if you don't, but fails (and the approach it uses is inherently error-prone).