Black screen when entering GDM login page

[殷啟聰 | Kai-Chung Yan]

Ubuntu version: Ubuntu GNOME 14.10 stable amd64
GDM version: 3.10.0.1-0ubuntu7
CPU Vendor: AMD
GPU vendor: AMD
Computer type: Laptop

After fresh installing Ubuntu GNOME 14.10, everything was fine and I installed fglrx. However after I reboot my machine it just stuck between the start screen (with GNOME's footprint in the center) and the login page. It was a black screen but the screen is on because I could see the backlight. However I was able to change to a tty by pressing Ctrl+Alt+F1 and after I installed LightDM and made it as default my machine successfully booted into the login page and everything was fine.

I think this is a bug related to GDM, fglrx, systemd and upstart.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: gdm 3.10.0.1-0ubuntu7
ProcVersionSignature: Ubuntu 3.16.0-23.31-generic 3.16.4
Uname: Linux 3.16.0-23-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CurrentDesktop: GNOME
Date: Sat Oct 25 16:42:43 2014
InstallationDate: Installed on 2014-10-24 (0 days ago)
InstallationMedia: Ubuntu-GNOME 14.10 "Utopic Unicorn" - Release amd64 (20141022.1)
SourcePackage: gdm
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.