In xfce 4.6.1 the Xkb plugin loses selected configuration (additional language - Russian, switching key - Ctrl+Shift, sign - text) once or twice a day. To make it work in Moblin OS (i686) I have to open properties and again specify the settings. On Fedora 11 (i86_64) settings window dissapears after trying to add additional language, it's possible to add any only after reboot.
xkb-plugin forgots settings on lid close. If laptop lid closed shortly or not closed at all, error not occur. xfce4-xkb-plugin 0.5.4.2-1 (Archlinux).
Should be fixed in git master branch, feel free to reopen if it still happens.