help!!! CSS on wordpress

hi
i just made a site in wordpress by customizing a wordpress theme. everything is done. my only problem which is also a big problem is that my meny bar doesn't show like it has to show. i opened my site on safari, opera, firefox and they look ok. but with IE the meny bar doesn't really look ok.

anyone who can help me pleaaaaaaaaase?
thank you :p

EDIT: by the way this is the link http://www.wereld-delen.be/wordpress/

I think....the problem seems to be in the scripting, not the css... I don't have the solution for that though....