Menus not showing up in IE6

Hi all, I've been building a site with some drop down menus in the header. It works fine in IE7, Firefox and (almost) in Opera, but those menus do not even appear in IE6 and I cannot figure out the cause.

This is the site: http://www.forware.es

This is my first site, so code might not be as clean as I would like.

Thanks.