That this issue is a very old one. There are thousands of posts out there and here's one with a few hundred.
I find that removing the devices in device manager and a reboot can bring it back but if not, but I think this has been covered before.
I have a Dell 5110 with a 4 GB flash inserted. Recently I got a message indicating that there was a power surge on a USB hub port and I should click "Reset" then remove the flash drive. I did this but now none of my USB ports appear to work. I tried the drive that was originally inserted on another laptop and it appears to work fine. That drive had been inserted in my Dell 5110 for over a year with no problems. Any ideas ?