Networks

are you using the client setup disks created at the server using the management console?

if there is a firewall running on the workstation, [????] it will prevent the workstation from joining the domain [blocked ports]. Are you trying to join the domain from Control Panel, System, Network Identification,Join Domain????? if the workstation was initially setup for a workgroup and now you want to join a domain, use the join domain option on the network identification properties in the system control panel. Make sure when you join the domain, you use the administrator account [or poweruser account].

I would say check your TCP/IP settings and make sure your dns is pointing at the DC.
Are you running Active Directory? If so the dns settings need to be set correctly.