Yeah I dunno man, no expert on Mac, but I got games to work on the Linux version, Windows version, and PS2 version of ScummVM, all without any problems.
And when I got the Linux version and PS2 versions to work, I had no idea what I was doing. I just followed the readme and bam, instant gratification.
Maybe its just because macs suck?
Did you lose this? It looks like a second mouse button...