I'm sure it is this empty div that is the problem.
<div id="right-half"></div><!-- #right-half -->
With the styling
#right-half{
z-index:-10;
position:absolute;
left:50%;
top:0;
width:50%;
height:100%;
background-image:url('pattern-right.png');
}
Safari and Chrome have problems with negative z-index and so the div is effectively 'covering up' part of the sidebar so you cannot access the links. If you try a link towards the bottom of the sidebar (that is below the offending div) you will see that these links work.
I've found that negative z-indexes are unreliable across browsers and I tend to avoid them now, using 'stacks' of positive ones instead