When I installed my Canon printer I tried downloading the drivers and got the printer working but I could not scan from the System Preferences > Print & Scan window. So I went back to basics and installed the software from the enclosed CD. After that it worked like a champ.
Also I had a temporary problem where my Mac could do test prints to the printer but could not queue documents to print. Rebooting my Mac and turning off and on the prater did not help. However unplugging the printer did fix it. So try that.
You can always write an email to Canon Care Center <firstname.lastname@example.org> asking if your printer is supported in Mountain Lion and from where you can download compatible drivers.
I found some useful Max OS X printer references in another thread: