what to do when this happens Because a USB device was drawing too much power from your computer, one or more of your USB devices have been disabled.

Small powered devices can get a small amount of power from the USB to run them, as welll as transfer data. Larger devices need to be plugged into the wall, and just use the USB for data transfer.

Unplug the device. Shutdown the computer, Wait 5 minutes for the USB port to be reset. Restart and before you plug that device back in again, first power it with the mains power supply using the adaptor, and then connect it to the USB.

What if this happens when nothing is plugged in? Like on my MBA 2013.

Hi,

I starting getiing this message today immediatley after I updated my firmware for my time machine/airport express base station. Could this be software related?

I have had no problems prior to this firmware update.

I am using an iPhone 5 and a Mac book pro from *cough* 2008 *cough*

update to the above (my edit has disappeared !)

This appears to be a problem with the USB cable. I can make this message happen during a sync with itunes. If i lift the cable with my finger about a cm away from the join between the cable and the USB connector head of the cable I get this warning message each time I try. I must have a loose wire/connection in the cable.

Thanks

I tried resetting my SMC and even brought my Mac to the Genius Bar. They ran diagnostics and basically one of my USB was fried. The message occurred in both Yosemite and El Capitan, so it wasn't an OS issue.

It's not a complete fix but it is a decent workaround. If you Disable Notifications and set it to start at 4 AM and end at 3:59 AM (how to do here: OS X Yosemite: Turn off notifications), you won't see the message anymore. It's not a fix, but it is a workaround if you don't care about seeing notifications.

Some low powered devices will only work well when hooked up to a wall powered USB hub. Also note, there has always been at least one low powered, and one high powered USB port on most Macs. Your System Profiler will tell you if you are plugged into one or the other with the device in question.

In my case it turned out that the USB-port was fried. Had to change the MBA's I/O-board. Cost me an arm and a leg since the shop where it was purchased accused me of damaging it myself. That's one shop where I'll never buy any products again. Ever.

What many people fail to recognize, is that USB is actually quite fragile. That's a thin piece of fiberglass with etched circuitry. As a result, any bending, pushing, shoving against the direction of flow in and out that it is designed to do, directly in and out can inadvertently damage the port.