I'm having the same issue with a couple of my USB devices. I have two Vista systems, one detects them, the other gives me an error?
A Cannon MP780 multi-function printer, a Patriot 2GB thumbdrive, and an iRock multi-card reader/USB hub. All of them previously worked, but just stopped, except the iRock, which works in USB1.1 mode. The computer knows it is USB2.0 and tells me to move it even though it's already plugged into a 2.0 port.