The subject behavior is almost always the result of the clients TCP/IP settings NOT pointing to the Windows 2000 DNS server, but to an external DNS that does NOT host the Windows 2000 domain.
To resolve this issue:
1. Control Panel / Network Connections.
2. Right-click the network adapter that you use to connect to the Windows 2000 domain and press Properties.
3. Select the General tab.
4. Select Internet Protocol (TCP/IP) and press the Properties button.
5. On the General tab, type the Preferred DNS server IP address.
6. Press OK.
7. Close the Network and Dial-up Connections Window.