Looks like the problem is in the "ul.MenuBarHorizontal ul" section of your CSS.
Here's the original:
margin: 0;
padding: 0;
list-style-type: none;
font-size: 100%;
z-index: 1020;
cursor: default;
width: 8.2em;
position: absolute;
left: -1000em;
Here's yours:
margin: 0;
padding: 0;
list-style-type: none;
font-size: 12px;
z-index: 1020;
cursor: default;
position: absolute;
left: -1000em;
font-family: Georgia, "Times New Roman", Times, serif;
color: #E4E4E4;
background-color: #E4E4E4;
The difference that seems to be making the difference is there is no width defined in yours. Try defining a width and see if that fixes the problem.
Abraham