NetBios over TCP/IP

The domain is Win2000 in NATIVE mode. All workstations are WXP pro. If I turn off use netbios over TCP/IP … especially on our member servers (same.. w2k) I get log on errors. Can’t find domain etc. If I do NSLOOKUP I get the sever name and IP. If I do the same for the domain it finds the name servers and domain. This runs into problems though when I try to find shared folders. I sometimes can’t as well as other domain computers.
What might be wrong.
PS. DNS and DHCP are fine.