You probably haven't followed carefully those threads I've linked or read my message well enough: that problem has been reported to be happening in FSX since 2006 when it was released and, according to those threads, it seems related to a corrupted saved flight.
As I've said, GSX doesn't affect in any way saved flight so, please, just stop losing your time chasing a possible GSX problem, because there isn't the theoretical chance installing GSX could affect a saved flight, because there's no interaction whatsoever between them, not even in read-only mode.
What other addons you have is entirely irrelevant, you can uninstall all of them but, if you have a problem with a saved flight, uninstalling all addons AND even uninstalling reinstalling FSX itself won't fix this, because saved flights are in your Documents folder, and this is not removed either by removing an addon or even by reinstalling FSX, you have to manually remove the actual saved flights files. And, a saved flight is NOT just a single file, but there are several files that made one, the situation itself, the meteo file and the flight plan (if you had one active when the flight was saved).
Again, this is just for your information but, it's entirely unrelated to GSX, which doesn't read, write or interact in ANY way with ANY of the things related to saved flights in FSX and, according to all the reports I could find (if you Google for it, you'll find several similar reports ALL of them dated well before GSX was released) it's always something related to a problem with a saved flight.
