Comment 3 for bug 1366165

also a Dell Studio XPS 9100 (with an Intel i7-930 quadcore) and an Nvidia GeForce 9800 GT, upgraded today from 12.04 --> 14.04

at the end of dmesg from startup:
[ 17.577900] init: Failed to spawn hybrid-gfx main process: unable to execute: No such file or directory
[ 17.769747] init: gdm main process (1182) killed by TERM signal

here's some info on the video card:
root@desktop-of-my-boss:/var/log# lspci -knns 03:00.0
03:00.0 VGA compatible controller [0300]: NVIDIA Corporation G92 [GeForce 9800 GT] [10de:0605] (rev a2)
 Subsystem: XFX Pine Group Inc. Device [1682:2372]
 Kernel driver in use: nvidia