Open Page Editor.
Navigate to "News and Events".
Select "Contact" component and click Edit button.
> Contact Chooser dialog is displayed but appears to miss some elements, it has no title.
Click "Select..." Button.
> A vaadin "Internal Error" message appears.

Stack trace shows:
Jan 7, 2013 4:32:18 PM com.vaadin.server.DefaultErrorHandler doDefault
SEVERE:
javax.servlet.ServletException: No UIProvider returned a UI for the request.
at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:312)
at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:201)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at info.magnolia.cms.filters.ServletDispatchingFilter.doFilter(ServletDispatchingFilter.java:123)
at info.magnolia.cms.filters.AbstractMgnlFilter.doFilter(AbstractMgnlFilter.java:91)
at info.magnolia.cms.filters.MgnlFilterChain.doFilter(MgnlFilterChain.java:83)