Looks like in the actual site, you have put z-index: 99999; into this block:
ul#cssmw ul.level-1 > li > a {
background-image: url("../cssmw_images/bg.jpg");
background-repeat: repeat-y;
border-bottom: solid 1px #9BB6D2;
color: #FFFFFF;
display: block;
font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
font-style: normal;
height: 14px;
line-height: 14px;
margin: 0 0 0 0;
padding: 6px 10px 6px 6px;
text-decoration: none;
width: 134px;
}
Make sure you also add position: relative; to that block as well. The z-index will not work unless the position is also specified.