[jQuery] Problem with Jquery Superfish in IE7

Hi all,
only in IE7 the submenu appear under my page's content.
I use bgframe plugin.

Here my code:
$("ul.sf-menu").superfish({
speed: 'fast',
autoArrows: false // disable generation of arrow mark-up
}).find('ul').bgIframe({opacity:false});

Do you have any ideas?

Thank you very much.
Bye
Z