[mod_python] mod_python.publisher problems: 404s on second and subsequent hits

I've been trying to get pubisher working using the example from the docs
(Chapter 6); I have "Hello.py" and the Apache config as in the docs under
section 6.1.1, running under Apache on Win32

The first time the URL is accessed everything works as expected. After that,
all I get is a 404 error until the server is restarted. I'm guessing I need
something to make the module persistent

Any ideas? There's nothing obvious in the logs, other than the 200 for the
first hit and 404s after that.

Thanks in advance,

Nick Barron
Manager, E-Services Division
Pennant Information Services Ltd -- Registered in England No. 3772667
PGP: A94C 4190 026E 3E02 6D50  C8FA 8620 3091 FF34 533D