About a week after release I ran the 10.6.1 update only to find that it had failed to install. I’m not sure exactly what happened since my typical method of carrying out updates is to click whatever needs clicked then move back to working on whatever other system is available. I do know that I was left with a dialog proclaiming that the update had failed and I should restart. Fine. I restart. Upon restarting the machine – my MacBook Pro circa 2007 – sat at the boot screen (grey screen with the little spinner) for at least 30 minutes. Not good. I restarted again but this time with the verbose boot sequence – Command-V at startup. Turns out the machine could not find a needed kernel extension for SCSI. Not sure why it needs SCSI but apparently the file was lost in the attempted update. It was clear that whatever happened the system was not going to fix itself, and Google wasn’t sure what was happening either as most the posts I could find related to the specific error talked of hardware failures.