[xwiki-users] Page tree stopped working on Main wiki

Hi, (disclaimer: new user here) I updated from 7.4RC1 to 7.4 (Debian packages, Tomcat7, MySQL). When I click the navigation arrows in the Main wiki, they come up empty. If I create a new wiki, it works fine. What could have happened here? Appreciate any help, thank you! Regards, Rodrigo