my car did this once before too. i took out the taillight bulbs and noticed that one of my taillights was filled with water. the connection was just coming off and on when i would hit the brakes hard enough or accelerate hard enough for the water to slosh into the bulb connection. drilled a super tiny hole in the bottom of the light so it would drain, and cleaned off the bulb and voilla! no more ubber ticky.
(fyi, the car ticks faster when there is a break in the circuit, or that switch is broke, for those that dont know this common knowledge)
