Dual Monitor's stopped in 12.04

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http://askubuntu.com – When I first installed 12.04, I used dual monitors with out a problem. I started getting intermittent problems, which happen almost every time now. When I plug in the second monitor, or start Ubuntu from Grub, both screens go black, with the mouse fixed at a the left of the external monitor. Sometimes this happens with the wallpaper tiled instead of a black background. Nothing changes until I restart the laptop. When I go into Settings > Default > Graphics, it says unknown under driver. I had no problems with previous versions. I am using Toshiba Satellite L500-19X. Does anyone have any ide (HowTos)