Can't print from XP Pro to printer on Vista network

I have two PCs running XP Pro, which are networked to a Vista Ultimate PC. The network works fine in both directions, but I am unable to print from the XP machines to my Canon Pixma MX700 printer, which is connected to the Vista PC via a local USB cable. Setting up the networking was problematic, but I finally got it working by setting up guest user accounts on all shared folders on the Vista PC. What do I need to do to network the printer?

re: Can't print from XP Pro to printer on Vista network

Have you made the Printer a Shared Printer? It explains how to do so here. You can even watch a video to learn how to do it! :-D

Greetings,
Nepomuk

re: Can't print from XP Pro to printer on Vista network

Yes, the printer is shared already.

re: Can't print from XP Pro to printer on Vista network

And (just guessing right now), do the guest accounts on the Vista PC have the right to access this printer?

Greetings,
Nepomuk

re: Can't print from XP Pro to printer on Vista network

Yes, guest priveleges are correct. When I try to print a test page from either of the networked XP computers, it says "Document failed to print: printer not responding," but it prints just fine on the Vista computer connected to the printer.