[Samba] Windows XP Samba PDC Login Problems

[S C]

*Getting grey hair by the minute*

Hello All,
    I set up a samba pdc for our office a month ago. All machines on the
network are Windows XP with a few Windows 2000 clients.

My Windows 2000 clients have joined the domain with out any problem. And are
having no problems with the PDC or the domain.

My Windows Xp clients have all joined the domain as well.  Though, sometimes
after a couple of hours, a day, a week, the windows XP clients cannot logon
seemingly out of the blue. This is not all systems. Maybe half run into this
problem as where the other half have given me no problems what so ever.

The following error I receive is:

"Windows cannot connect to the domain, either because, the domain controller
is down or otherwise unavailable, or because your computer account was not
found.  Please try again later. If this message continues to appear contact
your Sys Admin for help."

I am using Samba Version 2.2.3a (Comes with RH 7.3)
First. Yes I do have the sign or seal patch applied.  I also manually
checked the registry. It has been applied to the current control set and all
other controls sets just in case.

I have made sure the following in Local Security Policy is set:
  I edited or checked the following entries:
 "Domain member: Digitally encrypt or sign secure channel(Disabled)"
 "Domain member: Disable machine account password changes(Disabled)."
 "Domain member: Require strong (Windows 2000 or later) session
key(Disabled)"

Other questions:
Is the PDC down? NO
Are there other XP and Windows 2000 clients using the PDC at present: Yes
Do the machines have accounts? Yes
Were these machines working before on the domain? Yes

User accounts are located in the passwd and smbpasswd file
Machine accounts are located in the passwd and smbpasswd file as well.

The PDC is working.  Machines are using it.

I been digging around quite a bit regarding this, and it seems like I am not
alone.  But I have not found any answers or I have missed something very
simple..or maybe complicated.

Appreciate any help given

Cheers and Thanks
Sono