What was a wonderful scanner using Windows XP has now become a piece of junk suitable for an awkward doorstop. My Visioneer 9320 Scanner does not work with Windows Vista 64 Ultimate and the vendor website at http://support.visioneer.com/products/tools/OS/vista_Vis.asp explains that there are no drivers for Vista available for Visioneer scanners.
If you are in the same boat, I'd recommend that you take a look at a cheap alternative that will work. Canon's LiDE is inexpensive, installs easily, does not require a power cable (uses USB only) and works out of the box with Vista 64.