The Menu Bar no longer integrates with the Global Menu Bar on Ubuntu
I'm using Gnome Ubuntu 12.04 (I believe it's Unity,) and my Firefox Nightly build's menu bar (File, Edit, View, etc,) appears in a bar of its own. Here's a screenshot: http://i.imgur.com/Evbdo.png
I have already tried reinstalling firefox-globalmenu many different ways, but it seems that Nightly just doesn't want to accept it. (NOTE: My Beta build works fine.)
Opaite Mbohovái (1)
It works on my Canonical (18.0a2) Aurora; but I use Mozilla nightly.
I would just assume that there is not at the moment a compatible version of firefox globalmenu add-on available for your nightly.
I imagine you could ask there for an answer about when or if a suitable extension will be released.