I was having an issue where everytime I rebooted my Xubuntu 14.04 machine, in order to move my cursor to the left side monitor I had to drag my mouse to the right. I would open nvidia-settings with root access, make the change and save it to my xorg.conf file and think that I was all set. Nope, everytime I rebooted I had to fix it, so I finally looked into fixing the issue, I am not sure what causes it but you can clearly see within my Xorg.0.log file that it sets the screen layout correct but then later in the log it swaps them. So here's a little video I put together showing how I made the screen layout permanent. Enjoy