Comment 58 for bug 813343

Hi Radu, thanks for sending the information. As far as I can see there is only one thing that i don't understand in the xorg.log, when you try to add the second monitor.:

[ 310.430] (II) NVIDIA(0): Setting mode "DFP-0:NULL,DFP-1:1920x1080@1920x1080+0+0"

mine looks like this when attaching a display:

[ 37938.491] (II) NVIDIA(0): "DFP-0:1680x1050@1680x1050+1920+0,DFP-1:1920x1080@1920x1080+0+0"

As you can see, your DFP-0 is not configured.

All other things seem to be configured correct and all packages are up to date.

What I would suggest (not necessarily in this order)

1. Get rid of ALL old nvida related packages and reinstall them:

Boot into save mode.
See https://bugs.launchpad.net/ubuntu/+source/nvidia-settings/+bug/840462 (there #13)
Delete ~/.nvidia-settings-rc and ~/.config/monitors.xml (#45)
Reboot in save mode and reinstall nvidia-current and -settings.

2. You could you probably try the autoconfiguring tool Disper for nvidia cards ( https://launchpad.net/disper ) to get twinview working. On xfce you must enable an indicator message docklet to see the applet. But you can also use it from the command line (disper --help / man disper). On unity you have to add "Disper" to the list of allowed applets (dconf-editor->desktop->unity->panel).

Here is the package:
https://launchpad.net/~disper-dev/+archive/ppa/+files/disper_0.3.0_all.deb
(you can savely uninstall it afterwards)

Good luck