Account Login Loop Solution

I wanted to post this after a few hours of sweating bullets and failures to save others some pain and suffering.

The short story was my son was using my wife's MacBook Pro and it froze so he hit the power button. Afterwards, when he attempted to log into the one account that was created on that machine, the Finder would start to come up and immediately the screen would go blue and send him back to the login screen.

After much googling, reinstalling Snow Leopard and the 10.6.8 Combo Update, the primary account was still logging out immediately.

I deleted the /var/db/.AppleSetupDone file, and created a new admin account. After much struggling, I tracked the problem down to the loginwindow and Finder crashing when the original account was logged in. After a few more trial and error moving around of files, I tracked the problem down to a few corrupted preference files:

~/Library/Preferences/com.apple.recentitems.plist

~/Library/Preferences/com.apple.sidebarlists.plist

and I found a file with the same modification time that I had no idea what it was for:

~/Library/Preferences/pdb.plist

After moving all three files aside, I was able to log into the account.

I could have gotten to this point without the pain and suffering of completely reinstalling the OS and the combo update if I was able to track down that loginwindow and Finder were crashing sooner.

If you find yourself suddenly in the login-loop after a crash, my suggestion is to boot into single user mode, do the usual fsck disk check and mount the hard drive.

Then poke around /var/log and try to figure out what crashed at login. If you find that it's the loginwindow and/or Finder, then look at the last files in ~/Library/Preferences that were touched before your last system freeze/crash before you encountered the login-loop and move those files aside. I'll bet you'll be back up and running three hours sooner than I was.