I once shortcircuited my ps2 ports somehow, when unplugging the keyboard without shutting down first.

The ports worked fine after, but the mouse and keyboard were completely screwed, they worked fine for a while, then the mouse could suddenly start acting really jerky, it even seemed to store up movements I made and sort of send them all out in a burst so it seemed as if my system had gone mental, and it clicked buttons randomly too.

My keyboard just shut down some times at bootup, so I'd have no keyboard from time to time.

But unless you did that, and there were sparks or something, it's prolly interference.