mega menu sub-menu doesn't show up in Opera and Chrome

Hi Kriesi Support team,

site url : http://new.centrovelicotorreguaceto.it/

i have a strange behaviour of Mega Menu in Opera and Chrome Browsers

It works fine untill you scroll down in the middle of the page :
– when you scroll the page up, it works fine
– when you scroll the page in the middle, mega menu doesn’t show submenus area

It works fine with Explorer and Firefox
it doesn’t work with Chrome and Opera

i have installed “max mega menu plugin”, but i have the same problem deactivating the plugin and use it as a simple “mega-menu”

if i use it as a simple “menu”, it works fine in every browser

how can i fix it?

thank you