Horde change language fail in FC6

[akae]

Our clients are having trouble when selecting a different language than English for Horde/IMP. We manage to set the default selected language to Spanish, which is the desired one, but causes no changes in the Horde/IMP interface, showing all texts in English after and before login. Setting the language to Spanish in user's preferences at Horde also causes no change. We have no LOCALE problems with other apps. We have search all your KB, but he only related solution is for Debian/Ubuntu and cannot apply that steps in our system.
Thanks in advance and sorry for my poor English.