Introduction box on dashboard does not work anymore

I have configured an introduction box using 2.5b2 professional. After upgrading to 2.5 the introduction box is not displayed anymore and I can't even create a new one. Nothing happens if I select "Introduction" and click edit in the Edit Default Dashboard dialog. Deleting and creating a new one does not work either.

A different 2.5.1 enterprise installation with a database created from scratch does not work either. It displays the string "portlet.introduction.display.name" instead of "Introduction".