I had the same problem when I install FSX with SP1 and SP2. 5 minutes into any flight, I start getting blurry ground textures. I thought it was my ATi 5850 video card that was causing the blurry textures but I was wrong. I did a clean install of FSX without SP1 and SP2. After that I install FSX Acceleration. My FSX works fine now. I don't have any more blurry ground textures.