Can anyone help ?

We have a test LAN with a single domain controller and a single laptop. The
domain is
administered using Active Directory (AD) and we have fairly stringent GPOs
in place. I add the latop to the domain and everything seems well i.e.
seems to be picked up OK. However when I browse the laptop via the MS
Network using a windows explorer session on the server console I get the
"The account is not authorised to login from this station"
The odd thing is this doesnt always happen so I dont know whats causing
this. It looks
like an SMB negotiation issue...but cant see why would occur. I had this
problem previously
ona different LAN and fixed it by removing the laptop from the domain and
re-adding it.

Windows 2000 Server (SP3 + some patches)
Windows 2000 Professional + SP3 + some patches

Does anyone have any pointers.