Yes, - I see what you mean now.
The first thing to do before testing for any other causes, is to make sure that you have put the full 'DOCTYPE' declaration at the top of each page. Firefox and some other browsers may be able to render pages OK, but IE is fussy about this. The DOCTYPE declaration tells the browser what kind of language it's dealing with, and should be on all pages:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
I'm noticing that the pages that seem to be 'failing' are the ones where you have omitted to put the declaration at the top of the page (above the <html> tag).
Check that all pages have this included, then post back if there are still problems with the menu.