It's your #logo
that covers the menu. Either apply a width to the logo or z-index
to the menu. One of the below solves your problem.
Either this
#logo {
padding-left: 45px;
padding-top: 21px;
position: relative;
width: 360px;
}
Or this
#topNav {
display: inline;
height: 30px;
margin: 0;
padding: 0;
position: relative;
z-index: 100;
}