Sounds like a bad power supply to me. When the sim is running, and all your components are working hard, seems like the psu just can't keep up. Does your computer shut down with any other applications?
No Groundbound1 it does not shut down with any other application. I have never had a problem as described with either FS2000 or FSX. I think I am simply going to have to bite the bullet and backup all my aircraft files and delete FS9, and then reload.