...try unplugging the computer from all electrical sources and letting it sit for a half-hour or so. When you start it up again, it may spring back to life.
This happened to my brother when he disconnected his iPod. He thought his USB port was dead, and being his computer was an original Mac Mini with only two ports, this was a bit of a problem. He was hours away from buying a USB hub when I did a little googling and found the above solution.
Death to the USB Hub Industrial Complex!