I've uninstalled/reinstalled/updated the latest drivers for all usb ports. Also, the removable storage service won't stay on.
If you've already reinstalled, then I would have to atribute it to a hardware failure. Is this a new machine? I have heard of USB busses on motherboards dieing before, so it's not unheard of. I would try using a PCI USB card and see how far that gets you. As far as drivers go, I have never run into a situation where Windows required additional drivers for on-board USB.