Duplicate name exists on the network.

I’ve a NT 4.0 PDC & BDCs. I’ve mixed win95,98, winnt4.0 & win2k clients. I’ve DHCP & WINS server configured for name resolution.
Till now all the win2k clients configured with wins to connect to the winnt 4.0 domain. Now since last few days the win2k when they start display an error message “A duplicate name exists on the network” & they cannot Authenticate with the PDC. Due to which they cannot access any network drives. Still internet works properly & outlook email works fine. I’ve checked for any duplicate names in the network. Can anyone help in this regard ??? Pls. help !!!