[ubuntu] 16.04 LTS - Switching to nvidia drivers causes X to terminate after login

Hi,

I am using Ubuntu 16.04 LTS on an Acer Aspire V3-771G w/ Nvidia GT 640M (plus Intel onboard graphics/Optimus technology).

Nouveau works without issues. I also dual boot Windows 10 and use the Nvidia card via Optimus without problems there.

When I use the Additional Drivers application to switch to Nvidia 361.42 (proprietary, tested), after a restart:
- The login screen appears
- Attempting to login causes the screen to flash, an error message on a text console is displayed for a few milliseconds, and I am retued to the login screen.

How would we go about troubleshooting this issue?

Thanks!