I experience this very same thing, except mine is random at times. - I go to sleep leave my computer running, and when I come back the XFCE MENU no longer has any options, and right clicking on the desktop does not work either.
I must delete ./config/xfce/desktop/menu.xml - after that restart X and everything is fine again.... -- menu disappears after clicking "edit menu" https://launchpad.net/bugs/54509 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs