Perhaps it is the Ubuntu gui kit being used... I forget which one it is on Ubuntu, is it TkInter? You could try running another GUI program that uses the same kit. Most of the Ubuntu stuff uses Gnome...
Does the test listed in the following bug report work for you? Python/Tkinter fail Display test with Natty Unity https://bugs.launchpad.net/ubuntu/+source/python-defaults/+bug/749916 Chris
