there is an issue with canon scanners and the 10.6.7 update. I have been on the phone for hours with canon and they claim they can't recreate the problem on their mac's, but I read all over having issues. I use LIDE20 Canoscan and MP Navigator software, been using for years without any issues until the update.
I realise the same problems with my brand new MacBookPro 15", 10.6.7, and the new Canoscan 9000 and old Canoscan 8800 and also Canon MP750. I have to go back to my five years old PowerBook G4 (10.4.11) to scan and print!
Hope to see a solution soon.
PS when downloading or installing from DVD the scannerdriver, a window comes up saying:
"Cant't find TWAIN library in your system!"
When installing SilverFast from DVD this sign comes up, saying incorrect installing.
Was having similar problems. First, ran Disk Utility (see under heading: "Try Disk Utility") using Snow Leapord disc on startup and repaired disk and repaired permissions.
Then deleted the MP830 from the computer's printer list, and re–added it. Manually went to download and install the newest printer AND scanner drivers separately for the MP830 (on 4/17/12) from the Canon website.
Now, using USB to hardwire MP830 to my 15" Macbook Pro (10.6.8), Image Capture now recognizes it as a scanner and works perfectly using and selecting both the document feeder and the flatbed.
Hope this helps solve the problem for somebody.
I have been struggling for months, if not years to solve this issue. Even last week, re-installing the drivers and printers.
I just finished repairing the disk permissions (nothing was wrong with the disk itself), installed the drivers and printer again, ... AND IT WORKS LIKE A CHARM!!!!.
(Must be a problem related to disk permissions)
Thanks a lot Taylordesign!