In menu.css, changing the z-index in ul#cssmw0 li from 100 to 999 seems to work (testing with firebug).
ul#cssmw0 li {
background-image: none;
float: left;
padding: 0 0 0 0;
position: relative;
white-space: nowrap;
z-index: 999; /* Was 100 */
}