Alt + F2 : gconf-editor
/desktop/gnome/peripherals/keyboard/kbd
So, the problem was in $HOME/.dmrc file.
I don't know why, but the Layout field was changed to EN automatically (Layout=en).
It's because my system was configuring a new keyboard layout to USA after every reboot/logout.
I fixed it.
I have verified these files:
/etc/default/locale (OK) keyboard (OK)
/etc/default/
$HOME/.dmrc (Problem)
and
Alt + F2 : gconf-editor gnome/periphera ls/keyboard/ kbd
/desktop/
So, the problem was in $HOME/.dmrc file.
I don't know why, but the Layout field was changed to EN automatically (Layout=en).
It's because my system was configuring a new keyboard layout to USA after every reboot/logout.