Hi there, it may be the radiator fan not working and causing the car to overheat. Can you hear the fan working when the car STOP light comes on? If not, then a blown fuse might be the problem? Have you checked the fuses? If everything looks ok, then the next call is to let the dealer know that you've just picked the car and it is now overheating.
Good luck and let me know how things work out for you.