> I also noticed that there is a warning right before the exception is raised:
> 
> C:\Python26\lib\threading.py:803: RuntimeWarning: tp_compare didn't
> return -1 or -2 for exception
>   return _active[_get_ident()]

Right, it probably means the exception was raised before this very code
line, but wasn't properly signalled to the Python runtime.
Does the error disappear if you comment out the "with self.__lock" line?