I had similar problem (i used Polish, but only partially OS was translated). The problem is that app that control language settings in Freya i think is broken. Try to edit /etc/default/locale and add: LANGUAGE="fr_FR.UTF-8" LC_ALL="fr_FR.UTF-8"
then check results.
I had similar problem (i used Polish, but only partially OS was translated). "fr_FR. UTF-8" "fr_FR. UTF-8"
The problem is that app that control language settings in Freya i think is broken.
Try to edit /etc/default/locale and add:
LANGUAGE=
LC_ALL=
then check results.