Why did my RC-XD short circuit in Black Ops?
An RC-XD can be disabled by stuns and flash grenades much like a turret claymore, or other piece of equipment can. When your car is disabled it fizzes and becomes uncontrollable for a short period of time, this is temporary unless the car is destroyed while disabled.
You can do this to other RC-XD's by hitting it with a flash or stun explosion.