I have a client with the following details:
2 DC 2003 at the headquarters.
Several remote offices with XP workstations and NT4 File & Print servers (Remote offices at different subnets from the headquarters).
Every service and workstation is working correctly at the headquarters, they can contact the DCs, DNS and WINS, but none of the remote office machines can authenticate at the domain controllers from the headquarters, as a consequence, no services provided by the NT4 servers are available, and XP machines are login on with cached credentials only.
All tcp-ip communications to the DCs, DNS, and Wins servers at the headquarters are available, any machine from the remote offices is able to ping these servers at the headquarters.
This network made an upgrade from NT4 domain to 2003 on the last weekend, I can't confirm the remote offices were able to log on to the upgraded 2003 DCs at the headquarters after the upgrade, or if they have been login on with cached credentials since.
Someone tells me that they did manage to log on to the File & Print NT4 servers from the remote offices since the upgrade before these problems, but since It wasn't me, I'm not absolutely sure that is true. If that was true, and since NT4 doens't keep the credentials in cache as far as I know, this would confirm that they were previously able to contact the 2003 DCs at the headquarters.
I can't be sure the customer hasn't done any changes to the routers also.