There are some airports which cause FS to error out. Ascencion Islands is one, but also several near Saint-Maarten, St-Barth, etc. Actually if I fly from Martinique all is OK until I close in to these Caribean islands and then FS packs off.
Add-on scenery could do that. MS has some scenery bugs, I'm not sure if the patch they came out with cured it or not.
If you do use patch 9.1 follow it slowly step by step or it won't work.
You'll need a new crack (we have it for download) if you decide to use the new patch.
Actually I loaded an add-on scenery for these Caribean Islands and because I had this error I discontinued it, but probably did not respect the removal procedure to the letter and FS seems to be sensitive to this.
For Ascencion Island though this is way off the add-on scenery, but maybe the add-on scenery pollutes the database in random places as well.
I will try you recommendation with the patch but how do I determine which version I have. I believe I remember seeing this "9.1" string somewhere but can't vouch for it.
Follow the directions carefully, or it won't work...or worse.
I don't use it, everything is working well, why touch it.