If you’re using IE8 you’ll notice that some of the content in MOSS pages doesn’t work as designed. The issues will only occur if IE8 is rendering the content in native mode, which is only used in Internet zones. This is apparently related to some of the controls used to render the navigation. This is easily solved by rendering your site with an HTTP response header that tells IE8 to render the site in IE7 compatibility mode.
I added the HTTP response header to my MOSS internet site as described in this article and it now renders in IE7 compatibility mode.