So yesterday Apple released 10.5.1 and the update didn’t go so smoothly for me. This same thing actually happened when I updated Quicktime to 7.3 and iTunes to 7.5, after the install of the update Software Update told me that it had to restart my computer for the updates to take effect. So my MacBook began restarting and it never booted into OS X, the computer would cycle between the Apple logo and the prohibitory symbol at start up.
I tried everything I could think of to try and make the computer boot, I then resorted to booting up in Verbose mode (holding command+v at boot up). After doing so I realized that the kernel wasn’t loading. I had to do an Archive and Install of Leopard to get things working again. Luckily I was able to get everything working perfectly within just a few hours.
Like I said earlier this has happened twice, once with this update and again with the most recent iTunes and Quicktime updates. I don’t exactly know what is going on but I do know that from now on I’m going to back up my data right before every software update (I probably should anyway).
So back to the actual update itself. 10.5.1 fixed many bugs including improving the reliability of Back to My Mac-enabled Macs appearing in the Finder’s Shared Sidebar, improving reliabilty of iCal alarms that are delivered by email, many fixes for Apple Mail.app, etc.
I suggest that all of you go ahead and grab the update if you haven’t already but I do suggest that you have a full backup of your system before actually updating (you don’t want to go through what I went through).
A full list of the fixes for this update can be found here.