So apparently I helped break the login screen for a lot of non-English speakers in Ubuntu 12.04 recently. Sorry!

The basic symptom is that regardless of your system keyboard layout, you would get a “us” layout. Which likely meant you couldn’t enter your password correctly.

To work around this, change your keyboard layout to be correct in the upper right keyboard indicator in the login screen.

I’ve pushed a fixed version of unity-greeter to the archive (0.2.0-0ubuntu4). So once you do manage to log in and update your system, you shouldn’t hit this problem next login.