Users loosing Authentication Win2k AD

I'm looking for suggestions on how to trouble shoot user accounts in AD w2k.

Problem: Intermittent permissions lose. I user will loose permissions to access printers or OWA access and is forced to re logon OR they get can not find printer messages.

Setup: AD 2000 accounts in mixed mode environment. Users connecting to One Novell 5.1 fileserver via Novell client for windows logon with latest client for XP. All workstations running XP with occasional 2000 workstations.

I plan on mirgating off Novell and up-grading to AD longhorn when available.