NVidia TwinView on Ubuntu

After using envyng to install the NVIDIA drivers, I would get this error when trying to turn on TwinView:

Failed to set MetaMode (2) 'DFP-0: 1920x1200 @1920x1200 +0+0, DFP-1: nvidia-auto-select @1920x1200 +1920+0' (Mode 3840x1200, id: 60) on X screen 0

Even when running sudo nvidia-settings I would get this error, and things just wouldn't work.

Turns out the correct thing to do is to run sudo nvidia-settings, detect the second screen, and configure it as you want, and don't hit apply - instead hit Save to X Configuration File and then hit CTRL+ALT+BACKSPACE to restart X. This worked for me. Note that it will log you out and close any open programs you have. Now I have double desktops!