Notice to those running Mac Jaguar 10.5, Apple just recently (Feb 2008) released a further update:

About Leopard Graphics Update
Leopard Graphics Update is recommended for all users and improves the stability and compatibility of your Mac. This update requires Mac OS X 10.5.2.

Details include updated ATI graphics software.

It seemed to solve all my Myst V EOA problems. I was almost ready to give up, as I had crashed so often, even at the minimum settings. After crashing, usually during one of the speeches, the entire computer was frozen and had to be restarted using the power button.

This graphics update only applies to 10.5.2, and won't appear until after you install the upgrade to 10.5.2.

I haven't played an entire game yet, but it might be the fix we've been looking for. I've spent so much time lurking on these boards for the last few days, I felt obliged to let you know.

I only installed EoA a few days ago (using a slightly involved procedure for Intel Macs), so I'm not familiar with previous Mac/ATi issues.

I can report that my game is running flawlessly on OS X 10.5.4 (it's Leopard, not Jaguar ) with ATi X1600 graphics, so things seem to be sorted now. I'm not trying to make things easier for the system at all, running at native resolution (1440x900), shadows and reflections enabled, video and texture quality at max.

The game is surprisingly fluid considering it's running under Rosetta. Stability is rock solid, not a single crash so far. I've been to most of the ages and seen a number of "speeches" etc.