USB Device Not Recognized?

My approx. 3-year-old laptop's USB ports have suddenly and mysteriously stopped working. Every time I plug in a USB device, even though the device itself appears to turn on, a message appears reading, "USB Device not Recognized". I took it to a repair shop, where I was told nothing was wrong. In desperation, I attempted many methods proposed by other people with my problem. Unplug the computer and remove battery: No-go. Delete INF.CACHE1: No-go. It seems that everyone but me can solve this problem. Any advice?