Outlook 2003 Session limit

All our VPN users, OWA users, and Good link users are experiencing lock outs when they reach a maxium number of Mapi sessions and then are prevented from establishing another session. This is now becoming a weekly problem.

This has been an issue for sometime now and for a while we had been rebooting the server in order to reset their account. some believe this is a VPN issue, but most users are running different versions.

Has anyone else experienced this type of issue? Please help