The problem doesn't have anything to do with GSX, of course. It's a message from SODE, which usually indicates that:
- You restarted a new session of the sim too quickly after closing one, without giving it enough time to close all the running programs from the previous session
OR
- The simulator crashed or quit in a non clean way, so the sim could't close all the running programs from the previous session AND you restarted it too quickly.