Could you give me a link to the pygtk package you are using?

Sure: http://www.pcpm.ucl.ac.be/~gustin/win32_ports/pygtk.html .  I'm getting my gtk runtime from http://gladewin32.sourceforge.net .  Those are enough for me to be able to run gtk applications.  Let me know whether the extension at least works outside of inkscape.

Greg