XP Pro Logon to NT Domain

I have a new XP Pro computer that I named with an
existing computer account name on my NT 4.0 network and
since I restarted the NT server, it no longer recognizes
the computer by the same name. I can log on to the local
XP machine and connect to all network resources, but
cannot logon to the domain. I also have the same problem
with an older XP machine that I changed the name on, and
have tried numerous times to delete and re-enter the
account in NT Server Manager. Anyone else run across a
problem like this?