Major Issues After NT4 --> 2003 Upgrade

We've done over 10 test upgrades in VS 2005 lab, and just started the live
upgrade friday night. We've been dealing with a major issue not seen in the
lab. Basically, of our 200+ static IP servers, we're having to remove and
rejoin the domain up to 4 times for each server before they join correctly.
For some reason, the servers are joining the DNS domain name, instead of the
netbois name (which makes them not able to log into the domain).

Here is the scenrio:

Our NT4 domain we'll call "NBIOS" and the DNS domain name that we assigned
the new 2K3 domain we'll call ""

We had a BIND server that we set to forward to the PDC once we upgraded the
PDC and installed DNS on it. This way, we could take our time changing the
client static IPs that used BIND to the new AD DNS. This worked fine in the
lab. However, in the live we found that after a few hours and/or after
rebooting clients, suddenly they were saying that they couldn't contact the
doimain controller. We knew the NBIOS name would be remain the domain name
(showing up in the login dropdown) not the dns name, however, we were
finding that the clients started thinking they were joined to the
domain. showed up as the domain under computer properties (on the
clients that we no longer about to contact the DC). But NBIOS was still
showing up in the login dropdown. We're having to put the clients into
workgroups and then rejoin them to the NBIOS domain. Sometimes this works
after a reboot, but other times, even after it says "Welcome to the NBIOS
Domain", it would still think it was in the domain after reboot and
we have to change it and reboot again and then it would work. Sometimes we
have to do this four times before it works. We were awake for 56 hours
doing this over the weekend (200 servers) and still have many to go.

Why is this happening?

Dilerious, tired, desperatley looking for answers,