After opening a random website and inspecting a random element, the whole webpage turns dark, except for the inspected element. The main scrollbar also turns dark, which prevents scrolling the page. If you click on the the <html> element when in outline view, the scrollbar itself turns dark, which again prevents scrolling the page. The Web Inspector should never prevent scrolling the page that is being inspected.
<rdar://problem/5712788>
Fixed in r29887 <http://trac.webkit.org/projects/webkit/changeset/29887>