Firefox global menu missing

Binary package hint: firefox

The Firefox menu is no longer available as a global menu, and as this overrides window specific menu's it is not accessible via any means. Even the little Firefox button with the drop down menu is not usable.

I am sure this was working before, so it must be a problem with a recent update.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: firefox 4.0~rc2+build3+nobinonly-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-7.39-generic 2.6.38
Uname: Linux 2.6.38-7-generic x86_64
Architecture: amd64
Date: Mon Mar 28 10:11:21 2011
EcryptfsInUse: Yes
ExecutablePath: /usr/lib/firefox-4.0/firefox-bin
FirefoxPackages:
 firefox 4.0~rc2+build3+nobinonly-0ubuntu1
 flashplugin-installer 10.2.153.1ubuntu1
 adobe-flashplugin N/A
 icedtea-plugin N/A
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20110302)
ProcEnviron:
 LANGUAGE=en_AU:en
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: firefox
UpgradeStatus: Upgraded to natty on 2011-03-24 (3 days ago)