This game uses OpenGL which is known to have more driver problems (we use to have cross platform support).
I would suggest to all to start by resetting the settings as oulined in A.2:
http://www.frictionalgames.com/forum/thread-3754.html
Then make sure SSAO is off and see if that helps. It is good to know that you have some kinda of base-line where everything works as it should. And then from there start increasing, one setting at a time and see how the game works.
Regarding the lower resolution, yes I know it is a pain as you do not get a 1:1 game-screen pixel mapping, but since the game does not have sharp fonts or the like, it should not be that bad. Because of my crappy computer, I can run no games at native solution.