Everybody SAMBA!

[Tom H]

>> XP box and Ubuntu box connected via router (wired).  Router connected to
>> internet via cable modem (wired).  Both boxes are able to connect to
>> internet fine. Printer connected to XP via USB.

...

>> On the Ubuntu box, I've set up Samba and set several directories for
>> sharing.  I've got the Ubuntu box set as

> Did you get this sorted out?

The OP said earlier that a samba upgrade cleared up his problem.