[mod_python] mod_python mysteriously stopped working under Windows

I have this bizarre problem that is driving me insane. I had a working 
mod_python setup yesterday (W2000, Apache 2.0.47, python 2.3, mod_python 
3.1.0a - all vanilla). I needed to combine 2 projects so I set out to 
create a new project directory structure and ran out of disk space on 
the c-drive while doing something unrelated to mod_python/apache/etc. I 
cleaned up a few directories (again unrelated) and ever since then I 
cannot get even the simplest mod_python setup to work. I've tried 
uninstalling/reinstalling everything, even reverting to python 
2.2.3/mod_python3.0.3 all to no avail. No matter what I try (including 
explicitly setting PYTHONHOME=C:\Python23 and PYTHONPATH=C:\Python23\lib
\site-packages;C:\Python23\lib (among other combinations) I get an error 
in the log file saying "[error] make_obcallback: could not import 
mod_python.apache.". Note that python 2.2.3/mod_python3.0.3 just does 
not work at all, no messages anywhere - it is as if it is totally 
ignored. Note also that straight python cgi (e.g. pyblosxom) is working 
fine. At the moment I'm using the httpd.conf settings and mptest.py 
straight from the Testing section of the manual.

Can anyone shed light on this problem ?

Robert