So I completely reinstalled Skyrim the other day as I came back to it after a few months and my old version was crammed with mods. I've started a new, unmodded game with the HD DLC from Bethesda, but am experiencing all sorts of crashes and texture problems. Randomly, certain textures (NPC clothes/items/items in shops etc.) go all whitey purple. I'm not sure whether its connected, but my game also crashes randomly, with no warning whatsoever. I can run the game on ultra with the HD pack fine, at around 40FPS on average so I don't think its to do with lacking hardware; I have a brand new HD 7850. Is this a documented problem, or could anyone give me any advice to fix it?

Cheers