NT4 Domain Issues

I’ve found some info on this problem but no solutions. I can no longer add new NT based pc’s (Win2k, XP, NT4) to my domain. I can add them manually to the domain but still can’t add from the machine (even though it’s added on the server). Have triedusing different account other than Admin, same error, domain unavailable or could not be contacted. Packet Cap shows the PDC and BDC responding with SMB pacs stating that user is unknown. I’m down to planning a SAM restore as that’s the only thing left to try. Tried lmhosts, swapping PDC BDC, taking one offline blah blah blah. As a note, I can add same machined to other domains on our net. ANy other ideas before I start the drastic, dangerous stuff?