Whenever I click to run the program, the loading screen comes up, and usually a glance at the inside of the cockpit. After that, it freezes, and eventually the program turns my monitor off automatically. When I turn it back on, the screen is black, and is then automatically shut off again. So I have to then reboot my PC. I have a Compaq, about half a year old. I have tried unistalling, redowloading, and reinstalling a few times with the same result. The game used to work but does not any more.Any ideas?

My guess is that you were running FlightGear in fullscreen-mode (game-mode). Try running the program in window-mode instead.