Border is disappearing

On my site: http://www.hanle-productions.com/wordpress/ I’m having some problems displaying the border correctly in Firefox. If you look at it in IE7 it looks fine, the border starts at the top on both sites and goes down to the bottom. In Firefox the border disappears. But the strange thing is it is related to what posts are on the front page. Sometimes it shows up fine and other times it doesn’t…
Any ideas?