I received this error after installing updates and restarting the computer. It was nothing but a file-permission issue. You can easily fix it.
To solve it, type the follow these instructions:
Go to Application menu->Accessories->Terminal or press Alt+F2 and type gnome-terminal and press enter.
In terminal, type:
sudo chown username:username .ICEauthority
sudo chmod 0644 .ICEauthority
Replace username with your own username.
Restart your computer to check that the problem has been fixed.