X11 uses incorrect keymap after Kubuntu install

[p]

During the installation of Kubuntu 13.04 I selected to use the Finnish keymap. After installation I was unable to login via the graphical login prompt, but logging in via a text terminal virtual console was possible. After changing my password from the console to something only containing latin letters (which are in the same positions both on US and Finnish keyboards) logging in via the graphical prompt worked. When typing the character "-" instead the character "/" appears, which is consistent with the use of a US keyboard layout. Switching layout in the keyboard system settings module fixed the problem.

This bug completely breaks Ubuntu for many people as it leaves them unable to log in.