I just checked your page again and made the same change via Firebug and the menu does work!
However the way you have it set up makes the menu far too wide for your page design. At the moment you have 6 menu boxes with images at 200px wide. Therefore 6 x 200px is 1200px wide menu but your page design is only 921px wide.
So you really need to divide 921 by 6 and make your images and menu boxes 153px wide.....but if you had done that in the first place you wouldn't have discovered the problem...so thanks!!