Yes there is a bug after updating Fluida v1.5.5 : submenu is not working properly. See posts : 1.5.5. Submenu Not Working.
There is a temporary soltion proposed waiting a correct update, but i do not want to manipulate code of my sites (risk of crash). So i have to wait Cryout fix it as fast as possible becouse it is a serious problem.
Website: www.jeunes-lettres.org