Unwanted border/spacing... or something

Hey. I’m currently trying to clean up a site and make it validate HTML5. In the process I’ve hit a small snag that I just can’t get my head around.

Please remove both Xs.
http://www.meXdiadisplXays.tv/2012/

You’ll see above and below my navigation bar the are a few pixels of empty space that should not be there. This is the case in Chrome and Firefox, interestingly it looks fine in IE7. I would like the navigation tight against the flash header and the white box underneath. In theory the bottom of the navigation and the top of the white box should then line up against the background image.

What have i done wrong? Thanks in advance.