My mouse and keyboard keeps on freezing

[Lirange]

My mouse and keyboard keeps on freezing often. The computer is still running but my mouse and keyboard wont. Usually it's the mouse first then the keyboad after. I keep on having to unplug the usb's wait a while, then plug them in again. I've already defragemented my computer, fixed all the issues my computer had with tuneup utilities, but it's still occurring. How to fix it?