I just got a hold of Portal, but I'm having an odd issue with it: The game will not draw everything. Sometimes the boxes are invisible, and I just got to the level with the little motion sensing machinegun bots, but all I can see are their laser sensors, I can't see the bots themselves. I've tried changing the video settings, lowering the resolution, or details, but no luck. I'm on a MacBook running OSX 10.5.5 with 2GB RAM and a 2GHz Core 2 Duo. Any ideas?