In case any patrons call our desk about this problem here is the note from Janet Arth's e-mail of 3/4/08.
"Off campus users coming from behind a firewall may not be able to access the public catalogs at all. We are now quite sure this is a port issue and continue to work for a permanent fix. In the meantime, if the users can request that their local IT staff open port 8991 on prime6.oit.umn.edu, we believe this will resolve the problem."
-Daniel