Login looping, help!

[Maury]

MacBook 13-inch Early 2008, Lion 10.7.4, latest System Updates, 4 GB RAM, 500 GB drive

I recently tried to open an MKV under QuickTime on this machine. It apparently has Perian installed from a previous version of the OS, and when QT attempted to open the file, QT crashed. I force-quit everything, but this did not help, so I force-booted.

After rebooting, the machine entered a sort of "reboot loop". The machine would start up and then automatically log in to the main user account. Several Word documents appear, because the wife tends to leave everything open and running at all times. Shortly after, the screen turns translucent white, and then it all happens again, and again.

I stopped this loop by rebooting and Safe Mode. In this case you are presented with a login screen, and using any of the other user accounts on the machine works fine. However, when you try to log into that account, it crashes back to the login screen very quickly.

I can find various pages talking about the "login loop", but the actual solution seems difficult to understand. It appears there may be damage to a cache file, but how to address this from another login is not widely reported - I don't have access to the file in question.

 

[Maury]

According to this page…

http://junkheap.net/post/10504111960/solving-a-login-loop-in-mac-os-x-lion-due-to-corrupt

I need to delete/rename a corrupt file. Unfortunately it's not trivial to find out which one to kill, because there's different ones for each account.

I looked through /private/var/folders and found four subfolders, which matches the number of user accounts on this machine. However, it's not clear which of these maps to which user.

Worse, attempting to look in the C folders where the files are actually located only allows me to see into one of them - which I assume is the one for the user I'm logged in as.

So how can I see/delete/rename these files if I do not have access to them? Is there a way to force entry into folders?

That's assuming this is even the problem…

 

[Maury]

Ok, since that last post I have:

1) reset the PRAM (I think)

2) deleted the csstore caches in the private startup folders

3) deleted the Saved Application State

No luck. I do see that Word no longer automatically opens, so these changes have had some effect, but they didn't fix the problem.

I still believe this may have something to do with the old Perian install. It was the last version available - the machine was set to auto-update. Does anyone know where this file is located?

 

[chrfr]

Look for a file in her Home folder: ~/Library/Preferences/com.apple.security.plist.

Rename it and see if that solves the problem. I've run into this with a number of managed computer accounts in a computer lab where I work and deleting that file solves it. It's a stretch that it could be that, but it's an easy and harmless test.
What's happening is that the windowserver is crashing and logging her back out. There should be a crash log that will have clues in it.