Urgent Help OS X 10.4 login issues

Hi, I am Tom's mate with the problem.
The problem Mac is:
Model Name: PowerBook G4 12" 1.25GB Ram
OS 10.5.2, all updated

There are three accounts on the mac, mine, my wife's and an admin account we created. After three years sterling service its finally causing me a problem, wish the Servers at work were as reliable.
I was logged in running, Adobe, Lightroom, iPhoto, and iTunes. I was exporting processed images from Lightroom to iPhoto. The machine seemed to hang. After leaving it for about 30 minutes, I came back to see it still hung. I closed the lid putting it to sleep and tried to wake it up but to no effect. I powered off and on and tried to login.

I logged in but just got the wall paper of the desktop, after a few minutes the screen returned to the login screen. My wife can login on her account fine, as can the admin account. I have created a new account and it works fine, thats what I am using now as I type this.

I booted from my OS CD and ran a disk check which passed then verified the permissions, it indicated an issue with /Private/Var which I fixed. Still have the same issues.

Any idea's of an easy fix, or should I backup the users folder (full system was backed up about a month ago), re-install and try and set it backup.

I am a Mac newbie but know my way round a linux command prompt if someone can point me in the right direction.

Thanks, Richard.