Up until a few days ago when I plugged in the USB cable to my hub the drive was visible. Since then It will not show up. The motor is running, (I can feel the vibration since it is plugged into an outlet). I did try another external drive and that one came up fine. Does anyone have any advice as to what I can do? I only plug this into the hub when I need it and always leave the unit plugged into the AC outlet.