Oracle stops working after domain join

I have an Oracle 8 database running on a Windows Server 2003 computer which
is a stand-alone server; the Oracle DB works perfectly.

I'm in the process of building a domain and moving all servers and clients
into it, but when I join that server to the domain, Oracle stops working.

Actually, it's working fine (services are up and running), but any client
application (including those running on the server itself) can't no longer
connect to it; SQLPlus gives an error of "shared memory realm doesn't
exist". If I remove the computer from the domain and make it a stand-alone
server again, everything resumes working.

The domain is a Windows 2003 Active Directory domain, and I think the
problem can somewhat be related to the DNS suffix the computer gets
automatically after joining the domain; before this, it didn't have any DNS
suffix. The hostname and the IP address of the server didn't change, anyway.

Can someone please help me with this?

Thanks


Massimo

P.S.
I've already asked this on an Oracle-related newsgroup, but I was hoping to
get some help here, too.