Vista -> Server 2003 Writing Problem

I have a new Vista Ultimate machine that is unable to write to shared
folders on our Windows 2003 R2 servers. The servers are on the same hub as
another Vista Ultimate system that it will write to happily.

What happens is a 'Calculating Time Remaining' message window appears and
remains on screen for several minutes even with very small files. The file
that is written is always incomplete. If I try to cancel the transfer I
usually (but not always) have to reboot the system. Accessing (browsing or
reading) the shared folders from the Vista machine is sometimes slow but not
a problem.

I have applied the MS hotfix for the 'Calculating Time Remaining' problem
(KB931770), set the EnableLinkedConnections registry value for
authentication (KB937624), manually adjusted the NodeType registry value for
NetBt (KB938248) and applied the Vista performance and reliability update
(KB938979).

I am logged in as a domain admin. The folders in question allow full control
to domain admins. The new Vista machine replaces a Windows XP system where
the same login had no problems. The machine is connected to the network with
a Linksys wireless PCI card (the same one that was in the XP system) but I
have just added a wired connection while disabling the wirless. This has had
no effect.

The network has a single domain to which all machines belong. The network
route from the Vista machine to the servers is a little tortuous, but
involves fairly new hubs and a pair of fibre optic transceivers. (But like I
said, their is a Vista machine on the same hub as the servers which can be
written to without problems.) Access to the internet and access to the
servers via software such as Outlook appears to be unaffected.

Since the network is running behind a firewall and MS ISA Server 2004, MS
Firewall is turned off on the internal machines. All systems are fully up to
date with Microsoft Update.

Any help gratefully received.

Regards,

William