I emailed Canon and received an answer that solved the problems perfectly. I can now (finally) use my scanner AND my printer again!
See Below:
Dear Joel:
Thank you for writing to us. We value you as a Canon customer and
appreciate the opportunity to assist you. I apologize for the
difficulty you are having with scanning using the MP460.
It sounds like the old drivers for the MP460 are installed, and
unfortunately updating to the new drivers will not work until the
previous drivers have been removed. Please follow these steps to
uninstall the software:
1. Open Macintosh HD, Library, Printers, and drag the Canon folder to
the trash.
2. Open Macintosh HD, Library, Receipts, and drag any files that
contain your model number as part of the file name. NOTE: DO NOT trash
the CanonPrinterDrivers.pkg file.
3. Open Macintosh HD, Open Library, Image Capture, and TWAIN Data
Sources, and move Canon MPXXX.ds to the trash.
4. Click the Apple Menu, System Preferences, Print and Fax.
5. Hilight the MPXXX and click the minus to remove the print queue.
6. In the Apple menu, click 'Restart'.
7. When the computer has been restarted, click and hold your mouse
button on the trash can and click Empty Trash.
Once you have emptied the trash, please follow these steps to download
and install the latest drivers:
1. Visit Canon's web site at: www.canontechsupport.com
2. On the Consumer Products Home Support page, below the "Please choose
the model from the dropdown menus below:", select your model in the
following manner:
a. From the top dropdown box, click on the down arrow and select
Multifunction.
b. From the middle dropdown box, click on the down arrow and
select Inkjet as the product type.
c. From the bottom dropdown box, click on the down arrow and
select your model then click GO.
3. On the Support page for your model, click the Drivers & Downloads
tab.
4. Select your operating system from the dropdown box.
5. Scroll down the page and you will find all downloads available for
your model and the selected operating system. Click the link for the
file you want to download. When you select the printer driver, please
ensuer that you do not chose the printer driver labeled (CUPS).
6. Instructions for completing the download and installation will
appear on the page that follows. You will also see a Disclaimer at the
bottom. Review the disclaimer and click I Agree - Begin Download.
NOTE: Clicking I Decline - Go Back will take you back to the available
downloads list and you will be unable to download the file.
Please let us know if we can be of any further assistance with your
MP460.
Thank you for choosing Canon.
Sincerely,
Karl
Technical Support Representative