Anyone managed to fix this? I find it happens when the game's loading things, which is fine as long as I'm stuck on a loading screen but incredibly annoying when in-game. The game freezes for a fraction of a second, and at its worst this'll happen once every 2 or 3 seconds making it an unplayable mess. I've encountered the strange FPS drop people have mentioned here as well, but a simple Alt+TAB fixed that for me.
Running Win7 with a 7970 OC (beta drivers), an i5-750 and 12GB RAM. More than enough for this game.