gconf-sanity-check-2 exited with status 256

Terrible !!!

This morning, my Ubuntu 9.10 box message box showed 'gconf-sanity-check-2 exited with status 256' , and then I could not login my box anymore !!! But it's lucky, I could login as root.  Try to look for answers from google, but none of them worked !
[1] sudo chmod 755 /etc/gconf/*
[2] sudo chmod -Rc yenping:yenping /home/yenping

However, case [1] gave me some ideas, and I found permissions of /tmp becomes 755.
After below command, it works for me :)
[3] sudo chmod 777 /tmp

But I still have no more idea about that ~ confused !
Just keep records !