Thanks, I tried this. It took an age for FSX to restart and the scenery to load, but it didn't fix the issue. It's still trying to use the same AFCAD and the marshaller is still in the same (wrong) location.
That's not normal. The only possible explanation is, you MOVED KFLL in the Scenery Library, and now it has a lower priority compared to the default scenery.
The installer automatically put the airport on the highest level on the Scenery Library, but if you move it down, you'll risk causing conflicts between other AFCADs. GSX obviously respects the same priority as FSX, which means it will use the AFCAD of the scenery area which has an higher priority on the Scenery Library, just like FSX.
We had a couple of reports of people using 3rd party utilities to manage the Scenery Library, and maybe if you used such utility, the Scenery Library ordering has been changed, or maybe reversed, as if you changed the sorting order in a list, and save the list reversed from such utility.
Basically, the default scenery areas should be DOWN below, and the 3rd party airports should be on TOP of the list.