An idea of what the problem is, but not too sure I'm offering a viable solution.
If your client-workstation(s) aren't able to get onto the network and hook into the domain with the PDC (primary domain controller) it's most likely because they have lost their membership in the domain through a corrupted file. I use a utility called NETDOM that came with one of NT Server's Resource Kit Supplements. If you have the utility, you can go to a command prompt, and switch to the directory where it resides, and type <NETDOM help>. From there you will have to use a lengthy string of switches to logon to the PDC as Administrator and rejoin the domain. First you go to administrative tools on the Server (PDC) and open server manager. You remove the misbehaving workstation from the domain, then reboot the server. Go back to the workstation, and logon to the workstation local machine (NOT to the domain) and run the NETDOM command with switches, and when you go back to the server and reopen server manager, you'll see that the client has been added anew to the domain.
Here's the syntax for NETDOM, but I'm not suere that it's exactly the same for Win 2k as for NT 4.0.
http://www.tburke.net/info/suptools/topics/netdom_syntax.htm
Here's a couple links that will be relevant:
http://www.jsiinc.com/SUBC/tip1400/rh1468.htm
and
http://www.amazon.com/exec/obidos/tg/detail/-/0735608377/ref=pd_sim_books_1/002-0841998-8344854?v=glance&s=books
Incidentally, it says right on the box that you need the core kit in order to use supplement 4, but you DON'T.
Let me know if this advice is totally off the mark, and maybe I can refocus on what you do need. Some vague notions about leases and trust relationships come to mind, but I would need to read up on that stuff to offer further advice.
