Hello, I am having an issue with textures on some surfaces.

I have the graphics options maxxed at ultra on an i7, single GTX580, 8GB RAM, SSD machine with both DX11 upgrades installed. Everything seems to be running fine, apart from a lag in framerate when a lot of action is going on and some textures look "odd": They flicker with bits squares/triangles, especially at long-range (they look like shadows?)

Is this due my system spec; do I need to lower the settings? The card just meets the requirements outlined on the front page of this site, so I was wondering if there were any known issues?

If anyone could illuminate this issue for me I would be grateful.

Thank you.