Doesn't work on Mozilla

Hi,

I made a drop-down menu full compatible with ASP.NET and VB.NET

It works fine on IE6, but on Mozilla the drop-down menu hides when you hover 
a link from the list. It actually works even worse in Opera, the menus don't 
drop down at all.

The "Microsoft only code" I use is filter:opacity, but this is inoffensive 
to the behaviour of the menu.

The problem, I think, is in how Explorer interprets onmouseover an 
onmouseout

The menu is working here :

The only link it works is the Home Button

pwp.netcabo.pt/falmartins/index.htm

Thank you for any help