I have a Lenovo T510 laptop running Ubuntu 12.04 x64.
I can run dual monitors with my main display and internal, but not internal and displayport.
The displayport is connected to a dp to HDMI converter, which works perfectly in Windows.
In Ubuntu, when I connect the TV, the internal screen works, but the TV goes white, and the adapter gets really hot after a while. Also the screen doesn't show up in the displays menu even when I spam the detect displays button.
Also, according to Ubuntu, there are no proprietary drivers for this system. The card is a nVidia.