samba - Sep 2007 - Integrating Win2k3 into Samba PDC (on OSX 10.4.10)

I have a problem related to what I thought would be a fairly simple
procedure.

We have a working OSX Server 10.4.10 Open Directory system, with Windows
Services enabled via Samba as a PDC. We have joined approximately 20 WinXP
workstations to the Samba domain, and OD users can log into these systems as
expected (i.e. authentication works).

I have a Win2K3 server that was recently purchased and running the File
Server role. We have it joined as a member server to the OD PDC. I want to
set up the Windows Home and Profile directories so that they are located on
the Win2K3 server. File sharing is set up on the Win2k3 server and share
points are valid for local server users (verified via Windows Explorer).

When I log in to the XP workstation (using an account that has its home dir
and profile pointed to the Win2k3 shares) I am told that the user's profile
can't be found. Trying to manually navigate to the share points via the Win
Explorer or via DOS prompt fails, with an error message about a failed RPC
call and a possible permissions issue. The share points both are exported
for "Everyone" with read/write access.

Is it even possible to mount a Win2k3 share using a Samba domain user
account?

I did test this over the summer and everything appeared to work. Of course
now that I want to put this into production it's failing... Confused

Any help or insight would be much appreciated.
Thanks, jg