Yet another IE css weirdness

[eironae]

I've added a universal HTML header and footer to my site that are styled with CSS. This header/footer combo spans several dozen WP sites including a Revolution Pro themed site with no significant IE/FF issues. However, after applying the header/footer to my newest project the horizontal page menu disappears onmouseover in IE and doesn't return (no similar behavior in FF). I've no doubt it's my CSS as the template worked perfectly before applying my additional styles, but I was very very much hoping some wonderful CSS genius would take a look at http://nursing.southernarkansasuniversity.info and tell me if you see the culprit in quick fashion. I know just enough CSS to be horribly dangerous and trying to debug this could literally take me weeks.