[Evolution] Filters not executing reliably

["Alfred A. Lorber" <aalorbe sandia gov>]

I'm using Evolution 1.2.1 with Redhat Linux 7.3 and my inbox is on an
IMAP server.  I've set up a few filters for my incoming messages and
checked "Apply filters to new messages in INBOX on this server". 
Unfortunately, they filters don't always execute when I get mail. They
seem to work for a while (a few messages or so) when I first start
evolution, but then stop.  Whenever I edit the filters, exiting
evolution, doing a "killev" and restarting seems to be the only way to
get things going again.  To track what is going on, I wrote a python
script that does the filtering by subject for me and writes its status
to a log file.  I execute the script by selecting the "Pipe Message to
Shell Command" in the filter editor.  By looking at the log file, I know
the filters are not being fired every time I get mail. If I select mail
and do a "Apply Filters" the filters get executed just fine.

Any ideas?

Thanks
-Alfred