Hi, Just had the same problem suddenly arise on my 1996 406.Ended up having the car towed to a garage, being charged £175 to have ECU reprogrammed ( ? ), and now there is no immobiliser, ( keypad has been disconnected) and driver's electric window refuses to operate by the one touch buton. It has to be held down to operate.Central locking is now, also not functioning- just have to use key to lock. Key fob also not functioning. Has been a brilliant car, no probs until now, 78,000 mls. But quoted a fortune to replace or repair parts required. Sadly, not worth it now.
Allan Davenport, August 2007