I had the problem that in the context menu (on a website / in the tab itself ) all possible items where displayed.
i disabled all my addons and the bug was gone.
so i enabled them one after one. Firebug cosed the problem.
after some searching i found this bug:
Context Menu Displays ALL Possible Items
https://bugzilla.mozilla.org/show_bug.cgi?id=823072
and
Context menu shows all possible options when activated on HTML pages, and options do not work.
https://bugzilla.mozilla.org/show_bug.cgi?id=832022
so i searched for this bug related to firebug but did not finde something.
i deinstalled firebug and restarted.
installed firebug again and the problem came back. (as the https://getfirebug.com/wiki/index.php/I_found_a_Firebug_Bug! says :-) )
than i reseted all firebug options (with the firebug menu)
restarted and hey - its all normal now ;-)
so i just wanted to write it somewhere down so that if someone searches for something similar he finds a option to test out.
i have now idea what caused the strange behavior - i normally only use firebug as basic html css tool to try out some changes live...
sunny greetings
and funny debugging
:-)
stefan