What does the log say? Are you authenticating to the same firewall each time, or a different one?
I see this all the time. In my case it's cause by people who use laptops in the office, and while traveling, etc. The Novell client wants to talk to all the Novell servers we have. So the users winds up authenticating to each firewall we have as the laptop's Novell client tries to talk to a server behind each of our firewalls. It stops after a while, once they have authenticated to each firewall.
This behaviour may not be limited to Novell, any chatty client might do the same thing.
