Dont want to annoy you with silly questions of my own but have you tried all the usb ports on your computer? Also have you plugged other usb devices into the computer to make sure it is the port? Also what are you system specs?
The usb ports are screwy on my machine and even stopped funtioning all together on the back several times b4 I flashed my bios. The way I would fix my problem was reset bios and the usb would work again and I finaly fixed it permanently with a bios flash.