Doesn't happen here, and nobody reported it. Try all the following:
- Update your video drivers
- Reset the FSX settings to default, by removing the following file:
%APPDATA%\Microsof\FSX\FSX.CFG
This will force FSX to rebuild a new config with all default settings. After doing this, be sure you apply the HIGHMEMFIX tweak in the Addon Manager, save the settings and restart FSX.
If this still doesn't work, please clarify the problem, you said it happens at "some airports". Please, indicate all the following:
- The airport used. If it's not a default one, clearly indicate the scenery
- The airplane used. If it's not a default one, clearly indicate the airplane model.
- The Gate used.
- The GSX operation you selected.