I had the same problem after running the game for the first time yesterday.
The problem might be that the game does not properly adjust your video settings.
The first time I started I got a gray screen, I had to kill the process, killing the process did not change my resolution back but the game did start fine this time.
So my suggestion is to adjust your video resolution and try again. As a side note, I just tried it again and this time my resolution is changed on start and back to the way it was on exit(1280x720).
Good luck, keep trying it's well worth it!