Problem joining Win2k domain

I run a small QA lab, Win2k with AD. We decided to add a subnet to simulate a slow WAN link. I put three workstations in the subnet. The NT4 and Win98 workstations had no problem joining the domain. I get the following message when I try to add the Win2k Pro workstation:

Your computer could not be joined to the domain because the following error has occurred: The specified domain either does not exist or could not be contacted.

I can ping anything in both subnets. I removed and readded tcp/ip. If I add the computer in AD, the network wizard tells me that it exists.

What am I missing?

Rob