I created a new page named "Register", alias "register". I put some block content in the main content field and published my changes. The page that subsequently displayed, or my apparent just-created "Register" page looks like this:

http://chizeng.com/images/concrete_bug.PNG...
(or attached)

When I log out and view "Register", it displays the same empty page with the concrete bar at the top. This page is hosted with Dreamhost, which might have to do with it, but I don't know...