[Samba] Apparent Failing Trust Relationships with MSDN Windows XP

[Joe Swart - Gateway Absolute Data Dimensions]

Dear Samba List readers.

I have a working Samba PDC, and am using it (I have file access)
successfully with a Windows XP Pro machine. The PDC is from the Pink Tie
(i.e. Redhat) Linux 8.0 Distribution.

I am now setting up a second Windows XP machine to attach to the same
Samba PDC. I have chosen the computer name and domain on XP, and
configured them on the Samba PDC. If I boot up the new PC and login
locally as <local-XP-computer>\Administrator, then sure enough
<local-XP-computer> appears in the domain tree for my Samba-hosted
domain when inspected from my original, still working, XP box.

The problem comes when I try and log in to the new XP box with a Samba
user account, as opposed to merely attaching to the domain using the
machine account. If I type in a valid Samba account name, password, and
the domain name at the main new XP machine login, I get the message:
"Windows cannot connect to the domain, either because the domain is down
or otherwise unavailable, or because your computer account was not
found." It makes no difference what domain user account I try - even the
one that works fine on my old XP box does not work on the new one.

Alternately, but similarly, if I login as my local Administrator on the
new XP box, then go to:
Control Panel -> User Accounts -> Add...
Then type in a Samba user account name and the domain name I get:
"The user could not be added because the following error has occurred:
The trust relationship between this workstation and the primary domain
failed."

I inspected the <local-XP-computer>.log file on the Samba server, and it
has no information.

I am using the version of XP distributed with MSDN with Windows XP
Service Pack 1 (Express) installed.

I have tried setting:
My
Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\P
arameters\...
sealsecurechannel and signsecurechannel to zero (as per unofficial
HOWTO), but that seems to make no difference.

With thanks in advance for any help or suggestions.

Regards 
Joe