Comment 31 for bug 662077

I was having this problem with a new intallation of Ubuntu 11.10 Oneiric Ocelot, so any notion that the bug is fixed is a jump ahead of reality. Apparently, it is known exactly what needs to be done to fix it, but nobody actually gets it done so that the ordinary Ubuntu user with an up-to-date system is not afflicted by the problem.

What worked for me was to remove appmenu-gtk. For greenhorns like me, I may add that I did this in the Gnome3 desktop for Ubuntu 11.10 by clicking Applications in the main menubar, then clicking Ubuntu Software Center, and then entering
appmenu-gtk
in the search field in the upper right corner. That brings up a line with the words "Export GTK menus over DBus" on the left side. Click those words and a wide orange bar comes up with with a button labeled "Remove" on the right. Click that button.

This bug was not in Ubuntu 10.04 and seems to have been a by product of Ubuntu work on Unity. I do hope that you will get it really fixed soon.