Windows XP Pro Domain authentication

I have built a Win 2000 Server and set up a domain. I can join this domain successfully every time I try it from any of my workstations, though when I then restart the workstation and attempt to logon with one of the user accounts I get the error message ‘The domain is unavailable’

My DNS server is running ok on the server and all settings are correct. The DNS settings are entered correctly in the TCP/IP settings on the workstation.

Does anyone please have any idea what might be wrong here ?

Many Thanks in advance,

Owen Benneyworth