So it works if you restart, but once the game has been up once, it doesn't anymore?
You should get the game working once, and then change something inside the options menu as it's working and close it down.
Lets say if you run the game in fullscreen and a higher res, once you get on, go into the video menu, change it to windowed and something like 800 x 600 in resolution. And turn of the game from the menus. This will make sure it's saved I believe.
If you get the game to work, and it crashes, the changes you made in the game settings wont be saved I believe, might have something to do with that.
But I'm not sure.
The ogre.cfg should stay in a certain rendering mode of you change it.
Maybe it's not the game though?