I was able to solve mine by installing the latest driver from the Canon page. It actually wouldn't install properly so I unchecked every driver option (print, fax, etc.) and left only the scanner box checked; I figured I could print to another confi...
Same thing happening to me on the MF634C reinstalled updated drivers already, same thing. Seems like a lot of people have had this problem. It's impossible to duplex scan without it I hope they post a permanent fix.
