There's a strange lag in the menus and during gameplay

There's a strange lag in the menus and during gameplay; the keyboard and mouse stop registering. They register for a while, but then suddenly stop, either getting stuck on the last key I pressed or not registering anything at all. I've contacted live support many times, but none of them could help. I've tried many in-game settings, closed background application interfaces, and uninstalled and reinstalled GPU drivers. Still, it didn't fix the problem.