That looks like one of two things....
1) Your textures are messed up.
Or, in my opinion, the more likely of the two options...
2) Your video card is overheating or going out.
This is a form of artifacting, a term associated with video cards going out or overheating. I doubt it is the texture issue since when textures in FSX are corrupt, they generally render a specific color. I had the former happen not long ago, which unfortunately resulted in me having to purchase another hard drive. The latter I have also had happen, and it looks generally like what I see in the pictures.
Others are welcome to add their thoughts.
If you have a spare video card laying around, you might want to throw it in there just to see the results and confirm the issue.