Comment 4 for bug 1366165

I am also affected after upgrading from 12.04.5 to 14.04.1.

My system's facts sheet is as follows:

 - Lenovo T410i
 - Linux ubuntu 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
 - NVIDIA Corporation GT218M [NVS 3100M] (rev a2) (prog-if 00 [VGA controller])

Error log in /var/log/syslog contains at least the following messages:

init: Failed to spawn hybrid-gfx main process: unable to execute: No such file or directory
init: nvidia-prime main process (…) terminated with status 127
init: lightdm main process terminated with status 1
init: plymouth-ready (startup) main process (…) terminated with status 1
init: failsafe-x main process (…) terminated with status 127

The greeter won't show up, lightdm fails to start automatically and manually (via sudo service lightdm start) respectively.