I too have a single card "sapphire 5970 4GB" at first i thought my graphics card had too much memory, but then i thought it wasn't possible, the card doesn't require overclocking because it's dual GPU is fast enough and has the latest drivers (including june 2010 - DirectX) with the game crashing all the time (every 5 mins or so) it is really starting to annoy me. Every other game i have works fine.