When I first installed 12.04, I used dual monitors without a problem. I started getting intermittent problems, and now these happen almost all the time. 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 a Toshiba Satellite L500-19X.
Does anyone have any idea of how I could go about fixing this?