Vista Printing to Shared XP Printer

I am running into a problem where I have an XP machine that has a Dell Photo
720 printer attached to it via USB. I have been able to print to this shared
printer on the XP machine from a new tablet running Vista for quite awhile,
and then it suddenly stopped printing (while I can still print from the XP
machine).

I have downloaded the Vista driver from Dell, and installed it but it still
will not work. It states that it cannot communicate with the printer, while
I can see this device (the attached printer, shared drives, etc.). I do get
a message stating that it cannot communicate with the device.

To date I have tried the following, and none have worked:

Reinstalling the printer.
Adding a port to both devices (with the //computer name/shared printer name
setup). I read this was a fix in another post.
Stopped and started the print spool.
Downloaded the Vista Driver for the printer, and installed it on the Vista PC.
Disable bidirentional printing.

Nothing seems to get this working again.