We4ve just migrated a NT4 based domain to a Windows 2000 server, with new accounts and permissions (not sharing any information with the old server, IE, it was a new install). The problem is that after some time idle, computers (windows 98) lose access to the domain, cannot access any server or share, and cannot even re-logon (users have to restart their computers).
They're using static IPs, the WINS server is a NT4 server that also controls another domain. Both stations and the W2K uses that WINS. DNS is set to 127.0.0.1 on the server (clients aren't using DNS).