Yesterday Ubuntu 12.10 (32 bit) -the distro which worked best for me- gave me the lesson of my life. I was suddenly faced with the Log-in screen in spite of the 'auto login', and all my attempts at login falied even as a guest. I could only login via the command line after "Alt-Ctrl-F1" which meant there was nothing wrong with my password. I tried almost every suggested solution available but to no avail. The problem appeared after the latest package update which included 'Firefox'.
So, I am waiting for a miracle to bring life back to my dead PC.