I've had what may be a similar problem with my fight freezing for around 8 minutes. If I leave it alone it will resume flight as normal, otherwise it will crash. To keep this from happening I pull up Task Manager, find "fsx.exe" under processes tab,right click, go to "set affinity" and check mark only 1 processor to be active. It does make the scenery somewhat blurry but it stops the freezes and crashes. I read about this in PC Pilot magazine.