Chosen plugin : no close button in multiple select field

Hi all

I have a problem with the Chosen plugin : the close/delete button doesn't appear after each choice made in the multiple select field (the search icon in standard select as well but I don't care...).
It seems to be a theme conflict again... (tested with twenty ten : close button appears)

I posted a previous topic for another issue for which the reason was a theme conflict.
http://www.gravityhelp.com/forums/topic/front-end-user-only-when-clicking-on-the-submit-button-nothing-appens#post-74024
The last dedicated update (1.6.7) solved perfectly this AJAX issue but the chosen plugin issue is still here.
http://www.littledancer.fr/demande-de-renseignement/
in "Catégorie" filed for example

Thanks for your help (again!)

Done (image found in the GF plugin image folder)

Now it's working!
Thanks a lot