AppleTalk differences between NT40 and W2K3?

I have a customer who just put a new W2K3 server in his environment to take
the place of an old NT4 box that was mostly handling Mac file/print services
and logins.
I spent a good amount of time getting his file shares for Mac setup on the
new server, ensure that Apple Clear Text was the authentication method, and
finally figured out that they somehow had enabled RRAS to try to make it
work, so I turned that off and voila! they had good connectivity to their new
2K3 server.
However, they could no longer browse to the old server, and could no longer
mount the old server's shares on the desktop. Client environment is MacOS9
and OSX, flavors Panther and Tiger. It doesn't appear that zones were
configured.
Can someone think of a reason why access to the NT4 box went away once they
could successfully login to the 2K3 server?
TIA-