My guess is that you perhaps accidently changed the resolution in the game to a resolution that your monitor does not support (or don't have the res added in your driver).
Good call... my game was setup for 1440x900 (my previous monitors resolution) and my new Westy monitor did not support this by default. I added the res and the game loads now and allows me to change the in-game res. This is simply poor design on the games part, every other game I have reverts to 640x480 when this happens, allowing you to load the game and change to the desired resolution.
Thanks :)