Elly
Thanks for the tip. It worked. Mind you, after I finished the repair of the base version, when I tried to run the simulation, I got a fatal error. I then ran SP1 and still got the error. Then I ran the Acceleration Repair, and it fixed it up for good. The repair left all my scenery addons intact. Now all I have left to do is install my airplane add-ons.
Incidentally, before doing these repairs, I turned off UAC and my anti-virus.
Gaétan