The default Software Updater was not working correctly. It was giving the message "An upgrade from 'freya' to 'trusty' is not supported with this tool."
So I did:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
After the reboot I am unable to login. I type my password, the screen goes black as if it was going to login, and I'm back at the same screen.
I can tell the password is correct because when I type the wrong password, it gives that shaking animation. I even tried using the on-screen keyboard to type my password, so I know it's not a problem with my keyboard configuration or anything like this.
Also, I am not able to login with the guest account.
Can someone help me?