Reinstalling GSX cannot obviously make any difference to this.
From your description of the problem, it seems you started the GSX or the editor too quickly after starting a new session, restarting Couatl or switching airplane (which are basically the same thing), or when moving from airport to airport with the Go To Airport menu. It might take a while for GSX to start, especially if the airport has many jetways and, if you open the GSX menu when is still not ready, it will likely lock up.
We'll try to make some kind of check of not accepting any hotkeys before the program had completely loaded and generated all jetways in a future update but, in the meantime, you can use this method to know if GSX is ready to accept commands:
- keep the parking brakes set, on a gate
- do what you need to do, like moving to an airport, changing airplane, etc.
- wait for the TRAFFIC CONES to appear (don't use an airplane that has the GSX traffic cones disabled because it comes with its own), or the Fuel Manhole to appear (only if there's a jetway).
When you see either of the two above appearing, you can be sure GSX has loaded entirely and it's ready to work.