Forwarding this bug from Ubuntu reporter Beto1917:
http://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/899303

[Problem]
With xscreensaver set to random, once in a while it freezes for a couple seconds, recovers, and then displays the Apport window to report the lockup.  The i915_error_state file and dmesg indicate that a GPU lockup occurred, but the system recovered.

[Original Description]
crashed after xscreensaver started

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: xserver-xorg-video-intel 2:2.15.901-1ubuntu3
ProcVersionSignature: Ubuntu 3.2.0-2.6-generic 3.2.0-rc3
Uname: Linux 3.2.0-2-generic i686
.tmp.unity.support.test.0:
 
ApportVersion: 1.90-0ubuntu1
Architecture: i386
Chipset: gm45
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
Date: Fri Dec  2 14:37:51 2011
DistUpgraded: Log time: 2011-07-07 16:41:03.123900
DistroCodename: precise
DistroVariant: ubuntu
DuplicateSignature: [gm45] GPU lockup  EIR: 0x00000010 PGTBL_ER: 0x00000001 render.IPEHR: 0x60020100 Ubuntu 12.04
ExecutablePath: /usr/share/apport/apport-gpu-error-intel.py
ExtraDebuggingInterest: Yes, whatever it takes to get this fixed in Ubuntu
GraphicsCard:
 Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Acer Incorporated [ALI] Device [1025:029b]
   Subsystem: Acer Incorporated [ALI] Device [1025:029b]
InstallationMedia: Ubuntu-Netbook 10.04 "Lucid Lynx" - Release i386 (20100429.4)
InterpreterPath: /usr/bin/python2.7
MachineType: Acer Aspire 1410
ProcCmdline: /usr/bin/python /usr/share/apport/apport-gpu-error-intel.py
ProcEnviron:
 
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.2.0-2-generic root=UUID=34529bb0-121c-4f52-b1b7-6aca0f1c8e88 ro splash vga=789 quiet splash vt.handoff=7
RelatedPackageVersions:
 xserver-xorg             1:7.6+7ubuntu7
 libdrm2                  2.4.27-1ubuntu1
 xserver-xorg-video-intel 2:2.15.901-1ubuntu3
SourcePackage: xserver-xorg-video-intel
Title: [gm45] False GPU lockup  EIR: 0x00000010 PGTBL_ER: 0x00000001 render.IPEHR: 0x60020100
UpgradeStatus: Upgraded to precise on 2011-12-01 (1 days ago)
UserGroups:
 
dmi.bios.date: 09/08/2009
dmi.bios.vendor: INSYDE
dmi.bios.version: v0.3117
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: Base Board Product Name
dmi.board.vendor: Acer
dmi.board.version: Base Board Version
dmi.chassis.type: 1
dmi.chassis.vendor: Chassis Manufacturer
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnINSYDE:bvrv0.3117:bd09/08/2009:svnAcer:pnAspire1410:pvrv0.3117:rvnAcer:rnBaseBoardProductName:rvrBaseBoardVersion:cvnChassisManufacturer:ct1:cvrChassisVersion:
dmi.product.name: Aspire 1410
dmi.product.version: v0.3117
dmi.sys.vendor: Acer
version.compiz: compiz 1:0.9.6+bzr20110929-0ubuntu7
version.libdrm2: libdrm2 2.4.27-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 7.11-0ubuntu4
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 7.11-0ubuntu4
version.xserver-xorg-core: xserver-xorg-core 2:1.10.4-1ubuntu5
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.6.0-1ubuntu13
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20110811.g93fc084-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.15.901-1ubuntu3
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110411+8378443-1