[Mailman-Users] Duplicate messages and unpickling errors on Mailman lists after upgrading Mac OS X Server

[Alan Sill]

After applying the most recent Security Update to our Mac OS X Server  
10.4.10 installation, we are encountering the following two problems  
with Mailman lists hosted on this server that were working fine earlier:

1) Each message sent to any of our Mailman-based e-mail lists appears  
to be sent in duplicate to each member of the list

2) Under some conditions we encounter an "unpickling error" that from  
Googling around would appear to be a python error, as follows:

Aug 03 01:22:25 2007 (7442) Uncaught runner exception: invalid load  
key, 'm'.
Aug 03 01:22:25 2007 (7442) Traceback (most recent call last):
UnpicklingError: invalid load key, 'm'.

Aug 03 01:22:25 2007 (7442) SHUNTING: 1186122145.370055 
+f2ab5fac4a7b2dc159498a36ed5c91b5de42f490

The condition that produced this particular error involved sending a  
message to the "mailman" list on our server.

Any advice from anyone on either of these two problems? Is it  
possible that the security update left an old copy of mailman around  
with a different python, or is this a bug in the copy of mailman that  
we have in effect after the update?

We have tried disabling and re-enabling the mailing lists under  
Server Admin, stopping and starting the Mail service entirely,  
rebooting, stopping and starting mailman using mailmanctl from the  
command line, stopping mailman and running the check_db and check- 
perms commands and then re-enabling it, all to no avail.

Help would be much appreciated. How can I debug the duplicate  
outgoing messages problem?  Separately, is there a way to debug or  
repair the "UnpicklingError" we see?

Thanks.