[python-win32] PumpMessages in main thread called by embedded Python causes crash

[reckoner]

I have written some code that catches windows events that also includes 
the usual PumpMessages, and all of this works fine when I run it from 
the Python interpreter (Python version 2.6). However, when a separate 
application that has Python embedded calls the same code,  the calling 
application crashes. I have tracked this down to the PumpMessages call 
in my code.

My question is why does this work perfectly well from the interpreter, 
but cause a crash when called from the embedded Python running in a 
separate application. Note that I don't have access to the separate 
application in which the Python call is embedded and when it crashes it 
does not provide any kind of traceback.  It took a long time to narrow 
it down to the PumpMessages call.

Any advice appreciated. I am really stuck here. By the way, this is on 
Windows XP 32-bit.

Thanks!