I just reinstalled A3 from the CD onto my macbook, running OS X 10.5. The A3 version I installed was 1.1.1. I got through character creation without a hitch, but once I started the game the screen went black. I could still see the inventory screen, auto-map, and the buttons on the bottom of the screen without trouble, but the actual display of my characters walking around in Avernum was all black.
I then reinstalled the latest version of the game, 1.1.4 and had the exact same trouble. Note that the cutscene right before the game starts was also completely black, except for the text and little special effects (like the magical poofs).
I'd really appreciate any insights anyone has, thanks in advance.