04-22-2012 06:23 AM
Please make sure the used USB is no loner than 1.8m lengh and directly connected to a free port of the Mac.
make sure not to use ay USB hub or extention and also try plugging the cable to another port of the Mac.
If you have an iMac, also make sure not to plug the cable into the Mac keyboard which is not powered, but only to the ports at the back of the Mac.
If the same persists, I would recommend you to try replacing the USB and check for any change.
If my post resolve your problem please mark it as an Accepted Solution