A simple case to reproduce :
- as root, go to the Site management portlet
- Click on "Edit layout" then just save
- Click on "Edit Navigation" action in the Site management portlet but it seems the action request can not be finished.
I also have a look on the bug and i see that : after editing layout, the HTML fragment of each portlet rendered is missing a bound div with portlet id. That's why the sequent actions can not update the fragment of portlet to finish the ajax request