Vista 64bit/Samba connection problem

I have a LAN with multiple XP, Vista and Linux machines. Until September
29th the Vista Home Premium 64bit machine was able to map a network drive on
one of the Linux servers (using Samba). Sometime during the day of the 29th
the mapped drive disconnected and I have been unable to reconnect it.

Nothing was changed on the Linux box. Windows Update updated the Vista
system on the 29th and I suspect that something in the update(s) broke the
ability to connect. Prior to the breakdown Vista was passing the username
to Samba, after the breakdown it appears that it is not passing the
username. Samba logs and rejects an attempt from the user nobody (the
default guest user)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\LSA\LmCompatibilityLevel
is set to 1 (unchanged). The IP address of the Vista machine is allowed in
Samba.

Windows offers this as a fix:
Repair option: If you have access to this firewall then configure the
firewall to allow connections through TCP port 445. If you don't have
access, contact your network administrator or Internet service provider.
Click for more information about firewalls.

The Linux machine is not firewalled at all (evidenced by the failed
connection for "nobody").

I backed out the updates and that did not help.

Any suggestions as to where I could possibly fix this problem are welcome.