Need help with python and pyxml on AIX

[loial]

I have been asked to install a python application on AIX 5.3 that runs
OK on Windows
I have installed Python 4.2.2 from python.org and pyXML form
sourceforge.

However when I run the application I get the following error :

class xml.sax._exceptions.SAXReaderNotAvailable

Do I need to set some Python environment variables?

Can I test the availibility of this from the python command line. e.g
import something?

I am new to Python