Firebug display of css

In the HTML > Computed tab of Firebug, I used to get the list of user-defined styles, with the different competing values set from different stylesheets, with the overruled ones stricken out. Now I just get a flat list of all the values, irrespective of whether they are default or set by users, without the overridden values, and without the references to the stylesheets and line numbers. What happened? In the menu attached to the tab, I only have Sort alphabetically and Show Mozilla styles + options relating to colors. Search as I may I cannot find any option or setting to retu to the previous setup.