I'm really wondering if it is just the USB cable. My good USB cable was misplaced, and I tried 5 other USB cables earlier today (I wanted to confirm what mine said in the device manager). Anyways, I got the unknown device error when using these other cables. I guess I am out of luck until I find my good one or buy a decent one. I'm not sure whether I've tried the cable that came with the scanner or not. I have so many cord they just all get thrown together.