If you upgraded your Ubuntu into 11.04 / Natty Narwhal from Ubuntu 10.10, maybe you're facing multi monitor problem. Your second monitor will be blank or blink in black and this will surely happens when you're connecting the second monitor with your notebook that has resolution of 1280x800 (16:10). When this happen you don't see anything on the screen, no taskbar, no shortcut and no right click, you just see your wallpaper and your mouse cursor. When this happens and you're inside Ubuntu, do this :
