bad config: NoneType object is not callable

I have successfully installed PyMSNt and jabberd 1.4 on one
machine (Fedora Core release 3 (Heidelberg)) and that works
fine.

I tried installing the same packages on another machine (Fedora
Core release 4 (Stentz)), but when I start 
  python PyMSNT.py -D

I get the error
  Error parsing configuration file: 'NoneType' object is not callable
  Exiting...

This error occurs with either the exact same config file that I
used in the working system or if I just use the stock
config-example.xml from the distribution.

I suppose there is some mysterious (Twisted?) library missing,
but none of the installations complained.

Any suggestions?

Thanks,

Wendell