For what it's worth, I have the same issue with my 9950F when scanning 35 mm slides (I only use the scanner for transparency scanning). However, it only happens when I scan at 4800 dpi. 2400 dpi works fine in both JPEG and TIF with 48 bit RGB. I w...
I had the same problem. It appears that once you've installed VueScan, Windows won't accept the Canon Windows Vista driver. Once I uninstalled VueScan and deleted the scanner, I was able to run the driver install program (9950FVST6410324a_64EN.exe)...