Test simulation stutters on keyup/keydown so badly I can't test anything.

I'm on a fresh install of Unity, and for whatever reason, on any keydown/up, regardless of whether that key is bound to an action, the game will stutter for a fraction of a second. It isn't horrible once or twice; the simulation goes from 1000FPS to maybe 200FPS. But when trying to control a character or turn a car in the example project provided by the installer, the game will stutter to the point you can't see what you're doing.

I'm running:

CPU: Intel i7-4960X

GPU: Nvidia GTX 780 Ti

RAM: 64GB DDR3

OS: Windows 10 Pro

Any help would be greatly appreciated. I can't seem to find anyone having similar issues, especially with code that's supposed to be working right.