Multi-threaded printing and UIErrors in Windows

[Roger Binns]

My program has a random smattering of print statements
scattered throughout that are mainly a debugging aid.
They are typically things like this:

    print "entering key mode"

The code is multithreaded, and the printing typically
happens in both the main thread and a worker thread
doing serial port IO.  The problem I am experiencing
when the program is packaged up with py2exe is that
exceptions happen:

  IOError: [Errno 9] Bad file descriptor

This can happen in either thread.  Why is this
happening?  It doesn't happen on Linux or Mac,
and hasn't happened when not using py2exe.

Python 2.3, wxPython 2.4, py2exe 0.5 (and the
previous version).

Roger