Hi, sorry for necro-ing but I had the same issue as Ibex3050, though I am using an nVidia geforce gtx 550 TI
And I managed to get it resolved WITHOUT having to roll back any drivers.
So I thought that I would post it on here since it pops up on google search if others have the same issue
HOW TO FIX
Basically go to the game folder
Open the "obi.ini" file
Set the following values
You can go higher, or slightly lower, but avoid 640x480, as that seems to cause the game menu to bug out the nvidia drivers and crash.