You will need an Nvidia or ATI/AMD video card in your computer to run this game - an "onboard" or "integrated" chip will not work. If you're on Linux make sure to have the proprietary video drivers installed and functioning. On Mac cross your fingers that the Apple-provided video driver isn't bugged because you can't change out or update the drivers manually.
The ATI 4850 HD in my iMac under Mac OS 10.6 is able to run the game at 2560x1440 resolution on medium quality, but even then it'll stutter at times. If you only have an Intel video chip in your Macbook (or no 3D chip at all) this game won't run, or will have terrible framerates, or have all sorts of graphical anomalies. We can't fix that, your video hardware is too low-end to run this game.