I just bought Cod4 last night for my new macbook 13" i bought two weeks ago. I have 2 GB of RAM and Nvidea Geforce 320M graphics card. I'm using the option "optimal system settings" and still I encounter lag or freezing when playing single and multiplayer. Is there anything I can do to improve how the game runs? i'm not sure if its just lag or just freezing because everyone else on the servers usually has no lag, which leads me to believe its something wrong with my system. Tips?