Seems the 3d screensaver was to blame. After configuring the system to not launch any screensaver but just put the monitor to sleep the system didn't show the problem anymore.
My guess is there is a bug in the video driver that shows when the 3d section of the video card is used. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/560433 Title: [clarkdale] Xorg freeze To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/560433/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
