Logon Errors

We recently migrated from NT4 Server to 2 new Win2k Servers. Everything is working fine except, I have 3 users that can’t logon to the domain. The error that comes up on all of them is “username not found” and sometimes they can log in after severalattempts and sometimes not at all. One server is a PDC and the other a trusted domain. I have tried everything found on MS knowledge base without success. HELP ANYONE!..LOL P.S. These are all WIn98SE pc’s.