Ah, I have a similar problem!!! I have been using Samba for more than 5 years. All of the sudden, a couple of months ago, it didn't work for printing. File sharing still works.
Intuitively, one of those Microsoft updates may have affected things.
I've double checked my configuration files, both on the linux samba server, and on all the XP clients. The fact that ALL of the XP clients don't work now, and ALL of them worked without problems for a long long time, has me confused.
One thing I have found, which is different, is that the only way I get get printing to now work from the XP clients, is to attach them through http.
Where 192.168.1.5 is the printerhost, 631 is cups port, and MainPrinter is the print queue. That works, but treating the printer as a shared network device has somehow stopped working.
JUST TO CLARIFY: The URL entry appears to route printing to CUPS, whereas the smb or samba routing of \\sambahost\printer appears to use samba, and then route to CUPS.
The question remains: Why does samba not work, all of the sudden?