The problem is caused by the div with an id of col_box. If you look in the HTML, towards the top of the body you will see:
<div id="col_box"></div>
If you remove this, the page appears to look the same and you can click on links.
What happens is that this (transparent) div was overlaid on top of a large section of the body and thus you were clicking on it and not the link underneath it.
I don't know what it's purpose is or was meant to be, all I know is that removing it solves your problem, thus you should examine why it was there in the first place.