Comment 1 for bug 1392743

I'm affected by this bug as well.

Enabling multiple X screens when running cinnamon causes it to crash immediately on login, dropping to fallback mode. A reset of the Xorg.conf file is usually required to bring it back, but occasionally just removing the multiple X screens works.

Steps to reproduce on my system:
1. Install the proprietary nvidia drivers.
2. Open nvidia-settings.
3. Go to X Server Display Configuration
4. Set any number of screens to use separate X screens.
5. Apply the configuration by saving to X configuration file.

Cinnamon should now crash. If not, relog and Cinnamon will crash.

System information:
Nvidia proprietary drivers, version 361.28-0ubuntu1~gpu14.04.1.
Linux Mint 17.3 "Rosa" Cinnamon
Cinnamon 2.8.6
Linux Kernel v4.2.0-25-generic