I am having the same blue screen issue. I have a newish MacBook Pro, Intel running 10.5.2. I have had it for 3 months and it has been great. This week I did the auto updates and when it booted it stays at the blue screen, with a mouse arrow forever (I left it all night one night to see if it would go past with no success).
I tried booting in verbose mode and it runs for a minute or two showing me the command line initialization then goes to blue screen and stops. I tried clearing NVRAM, PRAM etc at boot and nothing helps. I tried booting into SAFE MODE and it would not go into safe mode, only blue screen for ever. I found article
http://docs.info.apple.com/article.html?artnum=306857 and tried option "C" first: booting into single user mode and running
/sbin/fsck -fy
/sbin/mount -uw /
rm -rf /System/Library/SystemConfiguration/ApplicationEnhancer.bundle
reboot
All of the commands executed and the fsck checked out with no errors but upon reboot, the same blue screen appeared.
I ended up getting out my 10.5 install disk and booting to that and re-loading the OS as described in the article and after reload it booted up fine and worked, with the exception that iTunes won't run because my library was created with a newer version of iTunes. I had a meeting using some critical data so I was relieved to up and running and went to the meeting. Afterward, I came home and decided to give the auto update a chance and let it update everything. Afer the update ran, back to blue screen. I am now RELOADING the OS again from the install disk. What is the problem here? I need help. This has taken 2 days of my life and is very frustrating. Should I not run auto update? Can I update iTunes to make it work but choose not to do the other updates? Apple, what is breaking my new Mac Book with the update?