Freeze in Ubuntu logo in boot

[Reason]
lightdm (light gdm) has some bugs. It is still in develop. So, suggest gdm instead of it.

[Solution]
1. Press Ctrl+Alt+F1 to get to a text-based virtual console
2. Uninstall lightdm and install gdm instead.

sudo apt-get remove lightdm
sudo apt-get update
sudo apt-get install gdm
sudo start gdm

3. When you fail to log-in,

sudo apt-get update

sudo apt-get install ubuntu-desktop

sudo apt-get install -f install

sudo dpkg-reconfigure ubuntu-desktop

sudo reboot

[Reference]

http://askubuntu.com/questions/175481/ubuntu-12-gdm-install-remove-problem

http://askubuntu.com/questions/205872/failed-to-load-session-ubuntu