Dynamic DNS problems

Im running a Windows 2003 AD domain with primarily NT workstations. I am also running DNS and DHCP on the server. My problem is that Dynamic DNS is not working. It simply doesn’t add the records to the DNS. I have all of the selections correct, such as unconditionally update DNS as well as for pre-2000 workstations. But it still doesn’t work.
I ran into this once before but there were two Win2K DC’s and I just set their own DNS IP’s to point at each other, and that fixed the problem.

However, in this case there is only one DC. Any ideas?

Brian