The function re_adminhead() checks the URL before adding the meta box, css, and js to the page. The admin URLs changed in 3.0, so they don't match the tests.
add_meta_box already specifies that it's just for pages and not posts, so there's no need to check the URL there. As for the js and css, I doubt there's any harm in including them on all admin pages.
If you delete those few lines, the plugin works great in 3.0.