I have the same issue, here's what I know:
1. The driver provided for these older lide units is a TWAIN driver
2. TWAIN is not supported in th edefault Windows fax and scan app bundled with Windows Vista and beyond (inc 7) and therefore another application is required that supports TWAIN (I use Irfanview)
3. Unfortunately the driver has never been ported to 64-bit by canon, so you also need a new driver. I've yet to come across one and have spent many hours looking along with a colleague.
Good luck, if you find a 64 bit driver let me know, these are great scanners and it's a shame they're not supported.