Close all your applications and go to text mode console by pressing Ctrl+Alt+F1
Login, and run this commands:
Finally restart your machine by running:
sudo service lightdm stop
sudo mv -v /etc/X11/xorg.conf /etc/X11/xorg.conf.bakold
sudo apt-get purge nvidia-*
sudo apt-get install nvidia-current
If you are still experiencing low resolution, it may be the monitor's fault. Try using pure HDMI, or DVI cable instead of VGA.
In any case of trouble, please post the content of this file after a fresh reboot:
Please paste it here: paste.ubuntu.com, and post back the link to it.
Let us know how it goes.