I agree Firebug can work in drop down menus, however it does not work (via right click) in the editor drop down menus for "font" and "size". At first I thought it was a bug with my install, however right clicking those drop downs at vbulletin.com has the same results ... nothing happens

However it does work here now that is very odd.
In regards to the css being called after addtional.css, how would I go about checking that? I don't recall seeing a reference to additional.css in Firebug.