I've had the USB power error on F14. It's not uncommon, still not seen anywhere where the problem has been diagnosed properly, but it doesn't happen often enough for it to worry me.
I just disabled one part of the USB3 device in device manager, error went away, and all ports still work.
edit: This was with Windows 7. I now use Windows 8 without any USB errors. Works perfectly.
Where about in device manager, a sreenshot would help. (for windows 7)
the xHCI is the USB3 on Windows 8.
latest usb3 drivers,not sure what controllers that board has so ive listed them all