I dont know whats going on but thats freaky. Im guessing either the computer is going nutz or maybe a sensor or two are reporting the wrong info, but then that should cauze a problem code. My guess is the software is encountering a bug somewhere in the code and thats why, but cant say for sure. could be worse, better to stoping the car randomly and than to accelerate it rite?!
good luck and carefull driving.