Rebecca, I'm surprised that your addition to the primary menu showed up on the login page and that just changing it to a relative URL fixed it.
Just so you know in case you see anything else strange with your login page -- I set up your site using the front page module -- see /admin/settings/front. Anonymous users see the page http://scrapexchange.nccommunities.org/front_page (note the underscore). Authenticated users see http://scrapexchange.nccommunities.org/frontpage.