Disable Alt+Space from activating the window menu in Ubuntu 10.10 Maverick

I wanted to change my Gnome-Do hotkey to Alt+Space, but it didn't work - when I pressed the key combination, it just activated the window menu. In order to assign this key combination to something else you must first disable it's current use. To do this, go into the main menu, then System > Preferences > Keyboard Shortcuts, and find "Activate Window Menu", double click it to assign it a new key combination, and simply press Backspace to disable it.