Screen switches off some seconds after wake up from suspend

[Michael Kogan]

I was running Xubuntu 12.04 on a Thinkpad X40 which has an Intel 855GM graphics chip. On 12.04 suspend worked flawlessly. Yesterday I upgraded to 14.04 and this broke suspend. The problem is like this: I close the lid, the laptop goes to sleep. After some time I open the lid, the screen goes on and if I'm fast I can even start typing in the password. However, some seconds later the screen switches off again, though I can hear that the system continues working. I can still switch to any TTY, only X has no graphical output. If I kill X from TTY, it starts again, I can login and then the system works as expected. In /var/log/Xorg.0.log I see following lines:

(II) AIGLX: Suspending AIGLX clients for VT switch
(II) AIGLX: Resuming AIGLX clients after VT switch
(II) AIGLX: Suspending AIGLX clients for VT switch

which exactly fits to my observations: On lid close the screen goes off, on opening the lid it goes on and then after some seconds off again.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: xorg 1:7.7+1ubuntu8
ProcVersionSignature: Ubuntu 3.2.0-40.64-generic 3.2.40
Uname: Linux 3.2.0-40-generic i686
ApportVersion: 2.14.1-0ubuntu3
Architecture: i386
CurrentDesktop: XFCE
Date: Sat Apr 19 19:39:18 2014
InstallationDate: Installed on 2013-04-27 (357 days ago)
InstallationMedia: Xubuntu 12.04.2 LTS "Precise Pangolin" - Release i386 (20130213)
SourcePackage: xorg
UpgradeStatus: Upgraded to trusty on 2014-04-17 (1 days ago)

[Launchpad Janitor (janitor)]

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