I suppose this is a simple question, but i just got my n900 a few days ago, i have yet a lot to learn

Anyway. My n900 rebooted during closing a game of Marbles, and it refuses to start up since. I guess something went wrong in the saving process... I can open the game and see the standard screen, but i can't start the game itself. Plus, i can't close the standard game screen either, when i've done this.

I DON'T want to reflash my phone, so i figured that re-installing the game might do the trick, only... how?