Re. the first crash ... was the unit that caused the crash right on the edge of the map, where it wraps around west-to-east? I know of several instances where strange things have happened at that 'edge' of the map, including artillery firing backwards, bombers attacking from the wrong direction ... plus crashes and hangs.
I don't think this is platform-specific, BTW, I suspect a basic logic error in the way the wrap-arund is handled in the Firaxis code, and this logic is ported lock stock and barrel to the Mac.
The second problem sounds more random, and if the first wasn't at the map edge then it, too, could be indicative of a problem in your installation. What version of the OS, and how much memory and spare disk space do you have? If you are running an old installation based on the original fragmented GOTM mods then it may be worth reinstalling Civ3 1.29b2, and using the latest All-in-One GOTM installer.