Try plugging it into a different USB port. I had the same problem, and my Front USB ports are acting up, so I plugged it into a rear port and it connected. Your USB port might be shot, damaged, or not getting enough power to support the usage of the device.
This wouldn't happen with USB 3.0 ports. Its goes from a power output from about 100 miliamps on a USB 2.0 port to 900 milliamps!