When I go to your home page and look at the source I see that one of the stylesheets being called is an IE-specific one. Do you know for certain how it is interacting with the styles in your normal stylesheet?
Also, there are two errors in the code which can cause problems. You have a meta tag inside a div, which isn't allowed and may be throwing the browser off. And there is a missing closing div tag down at the bottom, and interestingly it's the closing tag for the copyrightbox div. Try fixing that and seeing if IE gets the style right.
Rob