Op,
Have you tried changing the position of that absolute div on the right?
Code:
#rightcolumn{
width: 190px; /*Width of right column*/
/*margin-left: -190px; /*Set left margin to -(RightColumnWidth)*/
background: #FDE95E;
position:absolute;
top:0;
right:83px;
height:100%;
}
Increase the highlighted...it might help