Forwarding a freeze bug from Ubuntu user takashi torigoe:
  https://bugs.launchpad.net/bugs/475429
There are several other reports of freezes on 945G and 945GM in Ubuntu, but this seems to have more information.

[Problem]
GPU hangs on i945G when compiz is enabled. When compiz isn't enabled, 3D screensavers (especially euphoria) can make it hang. Bug is originally reported on Ubuntu 9.10, but has been verified with drm-intel-next kernel from 201001061342 and with the development verision 10.04 with xorg-edgers and the logs are taken from there.


[Original report]

Since upgrade to the 9.10 release, my screen freezes after visual effect (window move).
With visual effects disabled, there is no problem.
When freeze occurs, keyboard and mouse are unusable, but ssh login is OK.
So, I got Batchbuffer dump according to https://wiki.ubuntu.com/X/Troubleshooting/Freeze.
Dump is attached with this post.(dri_debug-20091105.tgz)

Operations
1. sudo INTEL_DEBUG=batch /etc/init.d/gdm restart
2. Set visual effects -> extra (compiz)
3. Window move by mouse operation.
4. Window swings (visual effect)
5. freeze occur
6. ssh & get Batchbuffer

I found that, when "Fusion-icon->Compiz options->Indirect Rendering" checkbox is on, 3D effects work.
compiz can disable the direct rendering by the checkbox.
But other applications (ex. 3D screensaves, blender, ... ) cause freeze as well as before.
It seems to be caused by kernel driver's lock, but it resumed by killing the freezed application.
I think that intel driver for i945 have some issue in the Direct Rendering function.

Kernel options that works
 acpi=off(nomodeset is no effect)
 no freeze, but there are some issue.
 - screen draw speed is very slow.
 - When compiz enabled, screen goes white blank.
    (Desktop Cube becomes white cube)
 - Render selection (direct/indirect) by compiz fusion icon is disabled.(fixed to indirect)

When trying older kernels, freeze seems to be introduced between 2.6.30 and 2.6.31-rc1, but using 2.6.30 seems to turn off direct rendering.

Architecture: i386
DistroRelease: Ubuntu 10.04
InstallationMedia: Ubuntu 10.04 "Lucid Lynx" - Alpha i386 (20091209)
LiveMediaBuild: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
MachineType: MICRO-STAR INTERNATIONAL CO.,LTD MS-7314
Package: xserver-xorg-video-intel 2:2.10.0+git20100108.4902f546-0ubuntu0sarvatt
PackageArchitecture: i386
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-7-generic root=UUID=e1d041b6-3b07-4d6f-aae9-5fbce8eee93c ro quiet splash
ProcEnviron:
 PATH=(custom, user)
 LANG=ja_JP.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.32-7.10-generic
RelatedPackageVersions:
 xserver-xorg 1:7.5+1ubuntu1
 libgl1-mesa-glx 7.8.0~git20100107.d699b672-0ubuntu0sarvatt
 libdrm2 2.4.17+git20091230.c5c503b5-0ubuntu0sarvatt3
 xserver-xorg-video-intel 2:2.10.0+git20100108.4902f546-0ubuntu0sarvatt
Tags: lucid
Uname: Linux 2.6.32-7-generic i686
UnreportableReason: これは正式な Ubuntu のパッケージではありません
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
XorgConf:
 Section "Device"
  Identifier "my-945G"
  Driver "intel"
  Option "DebugFlushCaches" "1"
 EndSection
dmi.bios.date: 07/14/2008
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: V1.1
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: MS-7314
dmi.board.vendor: MICRO-STAR INTERNATIONAL CO.,LTD
dmi.board.version: 1.0
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: MICRO-STAR INTERNATIONAL CO.,LTD
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrV1.1:bd07/14/2008:svnMICRO-STARINTERNATIONALCO.,LTD:pnMS-7314:pvr1.0:rvnMICRO-STARINTERNATIONALCO.,LTD:rnMS-7314:rvr1.0:cvnMICRO-STARINTERNATIONALCO.,LTD:ct3:cvr1.0:
dmi.product.name: MS-7314
dmi.product.version: 1.0
dmi.sys.vendor: MICRO-STAR INTERNATIONAL CO.,LTD
fglrx: Not loaded
system:
 distro:             Ubuntu
 architecture:       i686kernel:             2.6.32-7-generic