Connecting Printers

I bought a new Cannon all-in-one printer and connected it to my Comcast wifi (WPA) and my macbook pro laptop. It prints documents perfectly over the wifi connection. Then I hooked up my Mac desktop (10.5) and connected the USB into the printer. I downloaded and installed the drivers for the correct operating system, but it will not print. My Mac desktop is also connected to the Comcast router. I am confused that the desktop Mac will not print when it is directly connected via USB to the printer. Any suggestions are appreciated.

Have you tried running Software Update with it connected to your Mac ?

OSXX, the Mac's and printer are at my girlfriend's house. I will try it this afternoon. Thank you for the idea. May make sense. She is not good at keeping things up to date. Thanks again.

One more thought... do you think that I should try to connect the desktop over the wifi to the printer, even though the router is connected to the desktop?

I would leave it connected to your router so all can see and use it in your home.
This of course is after you connect it to your machine and do a Software Update since there is a possibility the wrong driver maybe installed at least through the update you will get the latest greatest.

OSXX... thanks again for your help. I checked for software updates but it still did not work. I called Canon Technical Support. The representative had me delete and re-install the drives and it worked. Thanks for responding and for your help.