Dns Problem?

Im running windows 2000 server, active directory dns e.t.c
I have a problem were by you can add a workstation to the domain ok, but after several reboots the name of the domain is resolved to the ip address of the PDC causing major network slow down.

Ie. Machine name was Machine.domain.dns
Is Now. Machine.10.1.1.1

There are no event log errors, and nslookup tells me everything is performing correctly. Yet the workstations have slowed down to a crawl.