Unsantiy has discovered why certain Macs become unbootable after an install that also includes updating prebinding. While there is a nasty bug in Apple implitation of updating prebinding, there is known only one way the bug can be triggered:
When “Optimize System Performance” appears during the update process do not touch your computer and definitely do not launch any applications. Just back away from your computer box as if it were a swarm of bees. Yes, it does mean that if you install the Mac OS X 10.4.9 update, you may get hit by the bug. More …