Menu Bug after Update !

Hi dear Kriesi team !

I have a super main menu bug after a live update :-/
The website is : http://www.lapetiterockette.org.

The main menu is displayed vertically on left side.
Nothing change if I switch off the plugins.

Here is my custom child css reported to menu. Nothing change if I delete it :

 /* _____ Padding Nav_Menu (espace entre lignes de base : padding: 1px 0 2px;) ______ */
  
.widget_nav_menu a {
  display: block;
  padding: 1px 0 2px
  text-decoration: none;
    }
   /* _____ FIN Padding Nav_Menu _____ */
   

   /*___________ Paddind main menu (espace en bas des listes de menu) ____________ */
  
  #top #header .avia_mega_div > .sub-menu {
    border-top-style: solid;
    border-top-width: 2px;
    display: table;
    padding-bottom: 10px 
    padding-left: 30px;
    padding-right: 30px;
    padding-top: 20px;
}
      /*___________ FIN paddind main menu ___________ */
      
  @media only screen and (max-width: 767px) {
.container #advanced_menu_toggle, #advanced_menu_hide {
display: none;
}

.main_menu, #header_main_alternate {
display: block;
}}

.main_menu ul.sub-menu {
margin: 0!important;
}

All the best,
R.