The problem you are having is due to the relative positioning on your #intro div, remove it. It creates a new stacking context and it is layering above the last link of the tallest dropdown. I see no reason for it being there, a lot of people will use relative positioning when they are unaware of what it actually does.
You also need to get rid of that empty div your using as a spacer, that's what margins are for. Just set 65px top margins on the two floats below your navbar.
margin:65px 0 0;
margin:65px 5px 5px;