It sounds like a GPU lockup. These are notoriously hard to debug. On -intel there are tools and such for doing so, but those don't exist for nouveau.
It is likely that this issue is fixed in a newer kernel since GPU lockups tend to be bugs in the kernel drm code. So, you might try just upgrading your kernel. Please test Precise (e.g. with a live cd), and if it still occurs there we can approach upstream about it. ** Package changed: xorg-server (Ubuntu) => xserver-xorg-video-nouveau (Ubuntu) ** Changed in: xserver-xorg-video-nouveau (Ubuntu) Status: Confirmed => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/574576 Title: [GeForce 310M] freeze w/ screen garbling (suspect xorg crash) [Lucid] To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-nouveau/+bug/574576/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs