Bodomi is correct, it's a problem with Adblock. There is a way to get around it without disabling Adblock, however, if you're averse to doing so:
There's an awesome Firefox extension by the name of Nuke Everything Enhanced
that allows you to remove any object from a page. You just right click on it and then click on 'Remove this object'. It works fine for removing the element on the front page that prevents you from clicking on the top few links.
Nuke Everything Enhanced also allows you to do things like highlight a bit of text or group of objects and then select 'Remove selection' or 'Remove everything else'. I find myself using it often to increase screen real estate or to get rid of annoyances. I used to use it to get rid of the damn smiley box to the side of the reply box until I just Adblocked those altogether. It's definitely one of my required extensions.