I believe that a lot of Mac users in the use of the process has encountered the following illustration of the hint: the USB device has been deactivated, unplug a device with too much power to re-enable the USB device. What is the reason for this? Small series through the network to collect and collate the following several solutions, hoping to help you solve this problem.
First, try resetting your Mac to the System Management Controller (SMC) as follows:
1. Shut down, plug in the power cord
2. Press and hold SHIFT, Control, option, and the Power key
3. At the same time, release Shift, Control, Option three keys, keep holding down the power key does not move until the boot
Second, if resetting the SMC still does not solve the problem, it is possible that the USB device has been shorted, you can try to replace the data cable. If it is a storage-class USB device, it is recommended to try one of the other similar devices.