I have three monitors in my system - all three are Dell E2014H 19" displays. One monitor is connected to a GeForce 550Ti, and the other two are connected to a GeForce 770, all via DVI. After installing Ubuntu (fresh install), the monitor on the 550 works as expected. One monitor on the 770 works, but the other has no signal. In Display Settings, all three monitors are shown, however the third monitor is switched to "OFF". Switching it "ON" and hitting apply brings up a generic "The settings could not be applied" message, and the display remains off. In NVidia X Server Settings, all three displays are listed, and have identical information.
The above has all been with both graphics cards using the Nouveau display driver.
When I switched both cards to the NVidia binary driver (331.38 from nvidia-331), the 550 remains functional. The 770 is listed in the NVidia X Server Settings panel, however the two displays on it are not listed in Display Settings, and the 770 has disappeared from the "additional drivers" panel.
Any ideas? This is on a fresh, brand-new install; I haven't even gotten around to putting my commonly used stuff on it yet.
P.S. - during the install process, the same behavior was observed - the 550 was functional, but only one screen on the 770 was on.
Edit: When using the XOrg drivers, the error "could not switch the monitor configuration: could not set the configuration for CRTC 64" appears on boot, and when attempting to enable the third display.