I always had trouble with that mission, sometimes it worked and sometimes not. I gather it has something to do with areas that the mission code requires for a "Pass" result on that node. If everything else works with FSX and this is your only problem than it's only with this missions parameters that is your woe.
One thing I noticed in flying a mission a few times is that one tends to think ahead of the mission and looking at the .xml one needs to hit the ten miles out trigger first to then hit the shuttle in sight one, in other words fly it like you would the first time(that you won the reward) so all the triggers get hit. Not sure if that's your problem but it's all that comes to mind.
If you think the mission is broken than as a last resort you can take that mission out of the folder and do a repair of FSX.