Hi there!
I'm having a similar problem as the problem I was having with Gravity Forms itself which is explained here:
http://www.gravityhelp.com/forums/topic/french-localization-breaks-form-editor-gf-151
Right now, Ajax functionality is broken in the "User Registration Settings" page. First, when I select a form to edit in the form select dropdown at the top, nothing happens. Works file in English sites. Secondly and probably related, if I have a "Registration Condition" set on an existing form or want to set a new one, the actual values for "Register the user if" (third dropdown) do not get loaded. The drop down remains empty no matter what is selected in the first two dropdowns on that line.
If it helps I put the language files here:
http://webfocusdesign.com/wp-content/uploads/2011/05/gravityformsuserregistration-fr_FR.zip
But I suspect it's something similar to the thread above which I believe was a bug in GF that was fized in 1.5.1.5.
