The Premiere Pro CS5 (5.0.4) update fixes the problem of crashing on Mac computers with ATI cards.
Premiere Pro CS5.5 doesn't have the problem.
Many thanks for stating unequivocally in this linked document that updates are cumulative!
I have asked for confirmation of this on and off ever since I first registered for these fora a decade ago. Even the acknowledged experts have not all spoken in unison.