You can try using z-index.
.vbmenu_option{
background: #ffffff url(http://i.wjunction.com/gradients/altBG.gif) repeat-x bottom left;
color: #64666a;
font: 11px verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif;
white-space: nowrap;
cursor: pointer;
border-top:1px solid...