I found the problem and was able to solve it: when I ran the arch command to import the old archives of the list that got moved to my machine, I ran it as root - and it set all the rwx permissions correctly, but failed to set the ownership settings correctly (owned by root rather than owned by mailman). After fixing this, it works again just fine. Lord praise the error log file :] To speed up changing the permissions correctly, I wrote a little script to handle it. it should work for any list you want. I've attached the script I made, feel free to put it in the bin directory. Th script will set ownerships to 'mailman:mail' (or mailman:mailman on the index.html link files) in the private archive area of whatever list you specify. This script should work without any problems on all basic installations of mailman. If you have special group, user, or path settings that deviate from the install defaults, double check this script before using :] hope it's useful to someone else too.
#!/bin/sh echo "What list would you like to fix the ownerships on: " read listname for file in `find ~mailman/archives/private/$listname|grep -v index.html` do chown mailman:mail $file done for file2 in `find /home/mailman/archives/private/$listname|grep index.html` do chown mailman:mailman $file2 done