I have had the exact same issues stated in this forum and others and have tried everything suggested, only to still not be able to print using my Canon MF4350d. I have a 2.93 GHz Intel iMac running 10.6.6 Snow Leopard. I've been extremely frustrated until tonight when I tried something on a whim and now am able to print again.
I'm not a "tech" person and I can't promise anything, but I know it worked for me. Here is what I did:
1. Open Print & Fax and delete any print queues that would be using the UFRII driver.
2. Open Finder and navigate to HD > Library > Printers > Canon > and delete the UFR2 folder.
3. Navigate to HD > Library > Launch Agents > and delete the file 'jp.co.canon.UFR2.BG.plist'
4. Navigate to HD > Library > Printers > PPDs > Contents > Resources > en.lproj > and delete the files named CNTD
**Z*2.ppd.gz (where
* indicates a character string that represents the printer model and 2 indicates a character string that represents the corresponding language).
5. With all of these files moved to the Trash, empty it and restart your Mac.
6. Go to the Canon website and download all 3 of the latest printer drivers - 2.15, 2.20 and 2.21:
http://www.usa.canon.com/cusa/consumer/products/printersmultifunction/black_white_laser_multifunction/imageclassmf4350d#DriversAndSoftware
7. Install the 2.15 driver and set up your printer normally thru System Preferences >> Print & Fax
8. You will get a warning saying something like "reinstall the driver software again, blah blah". ignore it.
9. Do the same thing and install version 2.20. I received the same message. I even deleted the printer in system preferences and reassigned it as well.
10. Finally, install the 2.21 version. No error message and about reinstalling the software. I did a test print and the job went thru just fine.
I also made sure that printer sharing was turned off, as well as the firewall in the security settings.
Anyway, it worked for me and I couldn't be happier. I was this close to buying a new printer. Worth a try, right?