the message low graphic-mode apear

[Tchapet Njafa Jean-Pierre]

GDM can't allow me to start my session. When GDM start a message tell me that the computer will run in low graphic mode.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: gdm 3.12.2-0ubuntu1~trusty1 [origin: LP-PPA-gnome3-team-gnome3-staging]
ProcVersionSignature: Ubuntu 3.16.0-29.39~14.04.1-generic 3.16.7-ckt2
Uname: Linux 3.16.0-29-generic i686
ApportVersion: 2.14.1-0ubuntu3.6
Architecture: i386
CurrentDesktop: GNOME
Date: Fri Jan 30 17:40:27 2015
InstallationDate: Installed on 2012-09-03 (879 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
SourcePackage: gdm
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.dconf.db.gdm: 2014-08-19T14:07:06.172489