I posted a message a few weeks ago about an intermittent stalling problem, the car would die sometimes when accelarating, braking or turning hard. After talking to a very helpful Bmw 'M-car' Mechanic, I was told of a very common problem with the M5 computer. The main power transister on the main logic board develops small cracks in its solder joints. The transisister is a very large plate that stands vertical with a large round transister mounted on it. It is held to the board with very few pins, these pins develop very small cracks in them that can only be seen with a magnifying glass. Resoldering these pins solved the problem. I saved $1000 with this information. If your car has the same problem give this a check.
Thanks to all who originally tried to help with the problem. Ken