I'm not sure why it is missing. We have only tested it on the standard Gnome/Unity desktop of the default Ubuntu, 32bit. One would think the 64bit would work as well. It seems to be missing sometimes with the KDE desktop as well.
Do the shortcut keys work there? Try F2 and see if the Master Control Panel will open. If so, that shows that the menu is open, just hidden.
Developer, Bible Analyzer
But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness. (Rom 4:5 AV)