After an update my machine won't finish rebooting, anyone know why?

Question

Hi there. I'm a pretty regular Mac user but I'm having a new problem. I installed a bunch of updates (its been a while since I last did it so there were lot) and restarted. It makes it through the gray screen and almost all the way through the blue, the progress bar runs all the way to 'Starting Mac OS X' and just hangs. Its been that way for a while, after about 30 minutes I got impatient (probably foolishly) and did a hard reboot - it does the same thing. If I listen to the hard-drive it doesn't seem to be doing much, every 30 seconds or so it make a little click - but it isn't reading.
Is this normal? is it doing some sort of pre-binding/maintenance after the install that takes a few hours?

Answer 1

There's no risk to repairing the drive even if the drive is OK.
Testing in safe mode would at least determine if the problem is related to something third-party particularly in startupitems or login items.
It also may be something as simple as a cache problem. You might try the following:
You will need to type some Unix commands. If you are not comfortable with this, I don't know of anything other than a re-install. But if you are careful, you should be OK. I recommend you print this out in a largish mono-spaced font so you don't miss any spaces (or add extra ones). Note that case is important.
Be careful. Some of these commands are dangerous, since you are going to be root.
Start up in Single-User mode by holding down the command (Apple) key and the 's' key while you press the power switch. You can let go the keys when you see white text on a black background. When this has finished you will see a prompt ending in '#', although there may be other messages. Type
/sbin/fsck -fy
followed by a return, at the prompt and wait a few seconds for 8-10 lines of output. If the last line says repairs were carried out, repeat this command until you get a message 'The volume <yourdiskname> appears to be OK'. Then continue with
/sbin/mount -uw /
cd /Library/Preferences
rm com.apple.loginwindow.plist
rm com.apple.windowserver.plist
cd /Library/Caches
rm -r *
cd /System/Library
rm Extensions.kextcache
cd /System/Library/Caches
rm -r *
reboot
This should now take you to a proper login screen after the normal boot sequence. You should then Repair Permissions by using Disk Utility (in your /Applications/Utilities folder).
If you get error messages saying files do not exist, note them carefully and just type reboot. Post back to say how far you got and what messages were output.