Ok, I think I got it working- but of course won't know for sure until next week (Feb 1) for certain...
I did a few things, but am not clear as to which may have helped.
Did the obvious things first, ran all the software updates, then ran a Disk Permissions fix (important). Then, I ran the "send reminders" script manually by typing 2 lines into the terminal, after navigating to to the Mailman directory. Directions for doing so are at
http://www.gnu.org/software/mailman/site.html (scroll to the bottom). After that, all my reminders went out (though not automatically, as I said, we'll wait and see on that).
However, other daily automatic messages started going out after that - including the bogus pending request messages (
http://www.python.org/cgi-bin/faqw-mm.py?req=show&file=faq03.038.htp) which makes me think its working now - since I wasn't receiving those messages before. But --we're using 10.4.4. So that could be different.