What happened in fact was that a graphics plotting function for monitoring got called twice frorm a different thread, due to an 'old' instruction inadvertently left. Due to the quasi random nature of the incoming data streams, this happened rather very sparingly. As the plotting itself involves quite a bit of code, there are probably several if not many reasons why problems could arise. It was never my intention to reenter this function and make it thread safe. Problem solved.
I was indeed a surprise for me to see Python quit this way. Thanks again for your commentary. malv -- http://mail.python.org/mailman/listinfo/python-list
