Comentário oficial
If you are having problems with the RB not being detected, please try using a different USB cable or a different port on your computer. As the RB is bus-powered, if it does not receive adequate power from the computer, it will not perform properly. Not all computers provide the same power to all USB ports, so you may need to change ports, or try a powered USB hub.
If the RB works on another computer, it's safe to say the problem is not the controller, but your computer.