I found that getSurveyInfo() in common.php calls makelanguagechanger(), this last function is defined in index.php so when getSurveyInfo() is called from the admin interface we have a fatal error (blank page), this happends at least in "Dataentry" and "export to an application". I don't know if this function intended to be available only for the survey taker or for the admin too, so I didn't touch it.