When I installed ubuntu 12.04 LTS, I carefully chose a login and password. A few weeks ago, I removed my password (setting All Settings, Login Options, "Password" to "None" and "Automatic Login" to "ON").

Since then, whenever I need autorization to execute an action (any updates requires authorization), I am asked for my password. The previous password is not working, nor is a blank password.

However, when I switch to console mode (via the <ctrl><alt><F1> command), the system only asks me for my login, not for my inexisting password, even when I'm executing commands with "sudo".