I think I know your problem. It's called NO ANTIALIAS. Remember when it happened to me after a useless drivers update. Useless because the old drivers worked fine, I am a knight of the: "if it works leave it the hell alone" and yet that time I had go and mess it up anyway.

Download Nvidia Inspector, or Ati equivalent, and assign to FS9 at least an antialias of 4X. And I suggest an as high as you can level of Anisotropic Filter without cutting (
too much) on the FPS. You'll see the improvements.

There is no such a thing as overkill. Only unworthy targets.