WinXP client can’t find 2003 DC

Ok I have client who has been running a 2003 Server with a Windows XP Pro clients for nearly a year now with little to no trouble. That is until recently.

They had hired another employee that required them to purchase another xp pro workstation. No biggie right? After adding the user and assigning the appropriate rights/privileges we obtain the following error upon logging in.

Can not find or locate Domain Controller….

which is odd as we can log in locally to the machine and browse the domain by logging in domainname\administrator

I have tried shutting off MS TCPIP Firewall to no avail.

Any insights, thoughts, suggestion?