Stefan, thanks for your reply. I believe you, but what confuses me is that it seems several people here have successfully installed and run bg2 on OSX. why didn't they have the same problem?
as it turns out, after some tinkering, the cd-rom problem has gone away. however, even though I can start the game and configure my play settings at startup, when it comes time to actually begin the game I just get a white screen while the disc spins. If someone who has successfully installed and played the game on OSX could post their crossover configuration settings for it and any little modifications they had to make, I'd appreciate that.
The copying of all four discs to the hard drive in the same folder for a full install was a good tip. it works around the swapping discs in the drive problem perfectly.
the entire problem here, though, may revolve around my using a macbook pro rather than a desktop mac. hardware and drivers differ somewhat in these respects. it seems more tinkering is required.