I can only think of three things it could possibly be.
1. The downloaded images are iffy, open them in an editor to make sure they're fine. It could be what you're seeing is exactly what's been downloaded.
2. Open the Nvidia control panel, find the image settings adjuster & set it to "let the 3D application decide".
3. If you're running the game fullscreen make sure you have the game set to run at your monitor's native resolution (or same as the desktop), for whatever reason it can cause issues for some people.
TBH I can't see a solid reason for it happening. :s