Fatal Python error: ceval: tstate mix-up

[gb at cs.unc.edu]

I just started (sporadically) getting the above message followed by
"The instruction at "0x77a7b0fc" referenced memory at "0x0000000c",
the memory could not be "read" in my python/wxpython-based imap email
client. I recently added a thread to handle posting messages to the
smtp server in the background. I'm careful not to touch the GUI from
the sending thread.

This is with python 2.1 on Windows 2000 with wxpython 2.3.

Any clues on how to track this down? The "Fatal Python error" part
makes it sound like an internal bug...

Thanks
gb