I cannot reproduce this, and nobody ever reported it before. I tried saving a flight at KCLT, and started/exited/restarted the simulator for at least 10 times, and there were no errors I could see.
Are you allowing enough time for the sim to completely shut down before restarting it again ? If you have many add-ons, this could take a while, even well long after the simulator icon has disappeared from the Task Bar. If you want to have a feel how much you should wait on your system, open the GSX Control Panel when the simulator is running, and note how much it takes for the "Compile" button to become available. That's when it's really safe to restart the sim again.