Ok guys. I'v been running Leopard on my wife's MacBook Pro since we got it in May. We have a Canon MF4150 attached to it via USB and have been sharing it out from the Mac. I have been using Bonjour and have been printing just fine from both my XP machine and my daughter's Vista machine. I just upgraded to Snow Leopard. I upgraded the drivers to the Snow Leopard compatible drivers from Canon and everything prints fine from the Mac. However, whenever we try to print from one of the Windows machine I get this popup on the Mac: "Canon UFR II Printer Driver Key value specified for ticket does not exist.: 15512" And the printer is now "paused" whatever that means. When I try to unpause it, I get that some popup error. I end up having to delete the printer and re-add it to get printing (from the Mac) working again. I've deleted and re-added the printer many times. I even went to far as to remove the drive on the Mac manually (according to Canon's directions) and reinstall. I've deleted/recreated the printers on Windows using the Bonjour wizard. Nothing has helped. Any help/suggestions would be greatly appreciated. Thanks!