If you have garbled graphics on the battlescape -- if you see strange shadows, or blocks that look like "dance floor patches", then please report what kind of graphic card your system has.
Apple Menu -> About this mac, More info, or Applications / Utilities / System Profiler
On hardware, click "Graphics / Displays"
So far, we have failures on an ATI Radeon 9300 and an ATI Mobility Radeon 9550, but success on an NVidia.
