[Mailman-Users] Mailman error when sending a message

I received this below error on one of our lists. I'm running Mailman
2.1.6. Do you know the cause of the below python error.

Dec 07 09:07:59 2007 (19091) SHUNTING:
1197043677.7637711+7717478d0c42f9abb211298207f5ffa813512bae
Dec 07 09:53:22 2007 (19091) Uncaught runner exception: unpack list of
wrong size
Dec 07 09:53:22 2007 (19091) Traceback (most recent call last):
File "/home/mailman/Mailman/Queue/Runner.py", line 111, in _oneloop
self._onefile(msg, msgdata)
File "/home/mailman/Mailman/Queue/Runner.py", line 167, in _onefile
keepqueued = self._dispose(mlist, msg, msgdata)
File "/home/mailman/Mailman/Queue/IncomingRunner.py", line 130, in
_dispose
more = self._dopipeline(mlist, msg, msgdata, pipeline)
File "/home/mailman/Mailman/Queue/IncomingRunner.py", line 153, in
_dopipeline
sys.modules[modname].process(mlist, msg, msgdata)
File "/home/mailman/Mailman/Handlers/ToDigest.py", line 92, in process
send_digests(mlist, mboxfp)
File "/home/mailman/Mailman/Handlers/ToDigest.py", line 133, in
send_digests
send_i18n_digests(mlist, mboxfp)
File "/home/mailman/Mailman/Handlers/ToDigest.py", line 315, in
send_i18n_digests
msg = scrubber(mlist, msg)
File "/home/mailman/Mailman/Handlers/Scrubber.py", line 266, in process
url = save_attachment(mlist, part, dir)
File "/home/mailman/Mailman/Handlers/Scrubber.py", line 411, in
save_attachment
filename = Utils.oneline(msg.get_filename(''), lcset)
File "/home/mailman/pythonlib/email/Message.py", line 724, in get_filename
filename = self.get_param('filename', missing, 'content-disposition')
File "/home/mailman/pythonlib/email/Message.py", line 607, in get_param
for k, v in self._get_params_preserve(failobj, header):
File "/home/mailman/pythonlib/email/Message.py", line 554, in
_get_params_preserve
params = Utils.decode_params(params)
File "/home/mailman/pythonlib/email/Utils.py", line 337, in decode_params
charset, language, value = decode_rfc2231(EMPTYSTRING.join(value))
File "/home/mailman/pythonlib/email/Utils.py", line 284, in decode_rfc2231
charset, language, s = parts
ValueError: unpack list of wrong size

Dec 07 09:53:22 2007 (19091) SHUNTING:
1197046400.9411609+1cf11358e8862eae84391721d8fe3f1fae53d614