Don't get me wrong, I don't mean to discredit you. Microsoft software certainly has (more!) than it's fair share of problems. Just to give you an idea of the point I was trying to make though. A while back when Battlefield 1942 came out for computer, I would constantly get random lockups and bluescreens. Up untill this game, I had never had any problems with my computer in ANY game. I spent countless hours trying to troubleshoot the problem, untill I ran memtest and found the program would halt within only a few passes of stressing my memory. The culprit turned out to be one of my dimms. I replaced both dimms with some higher quality Corsair memory, and then my problems vanished, period. My existing memory had been fine (and still would be fine) had I done anything else with it, however, battlefield 1942 in particular exposed a weakness in the hardware that other programs hadn't at the time. As such, even though your computer may work great with everything else, sometimes, flaws or faults in hardware are exposed by programs depending on how they stress them.

Either way, it's a moot point. This certainly isn't the only cause, something as simple as different hardware combinations can cause problems. Sometimes, the solution to problems with PC's don't even make sense. And yes, sometimes (probably more often than it should happen) it's just a case of shoddy programming. But the FS series of games have always been pretty stable, even by history. If you keep having problems, try to locate an online community of MS Flightsim users, more often than not, if it's a common bug with the game it's self, you will find your solution there (or, if nothing else, other uses with the same problem, showing that it's not only you). If nobody else seems to be having the same problem you are, i'd look to your hardware, and not the software.

Hope i've been of some help .