Theme Horse

Hi djelal,
I just tried in my demo site with 15 submenu and all is working fine. I test after 10 + items also but no any issue found. I think there may be some plugin issue too. Once deactivate all the plugins that you have installed and check whether your menu is working fine or not. One thing did you customize any code or any CSS ? If you have change then once make a backup and test it whether it works or not.
View this Url its working fine here.
http://awesomescreenshot.com/0ad3s59hfb

Thank you!