First off, I had one hell of a time trying to find this product. The American Audio site isn't too user friendly in my opinion. That and the fact that I would not have considered this to be software.
The answer appears to be very simple: It appears that this device isn't supported for VISTA.
Downgrade/upgrade to XP Home or Pro and enjoy a faster machine and a better computing experience.
On a different note, perhaps this was not a well selling product so that is why they are not supporting it for Vista, or maybe they just haven't rolled new drivers for Vista yet.
What I really would suggest is not USB, but rather S/PDIF and a pro audio interface if you intend to transfer your recordings. Why? Well, the pro audio interface will have much bette drivers. With going S/PDIF(assuming your turntable has this feature, only one does to my knowledge and I have it, it's a Numark TTX), you're guaranteed a true clocked signal that is already properly optimized and calibrated properly and you avoid the groundng issues better than via USB.
Plus, depending on your computer, your USB bus, which you need to know taps more resources than Firewire, can be prone to clocking issues. Bet you didn't think about that, did ya?
There are other cost-effective solutions that involve a device that is a RIAA EQ curve phono pre with a USB interface that you can choose to go with, some even as lost as $35 or so. I would say you don't need to spend more than $100 on a replacement device should it come to that.