boot fails due to null pointer dereference in drm/radeon

9 times out of 10 on this PC, the boot process fails with a null pointer dereference in DRM.
It boots as far as a login prompt and I can login but the whole system hangs within a few minutes.
This sounds extremely similar to 549476 however I was asked to open a new bug rather than re-open that one.
Adding nomodeset to the boot parameters makes the boot process complete successfully however the splash screen while booting is shown at a strange, low resolution and prompts for passwords aren't really visible.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: linux-image-2.6.32-22-generic 2.6.32-22.33
Regression: Yes
Reproducible: Yes
ProcVersionSignature: Ubuntu 2.6.32-22.33-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-22-generic i686
AlsaDevices:
 total 0
 crw-rw----+ 1 root audio 116, 3 2010-05-17 10:10 seq
 crw-rw----+ 1 root audio 116, 2 2010-05-17 10:10 timer
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.21.
AplayDevices: aplay: device_list:223: no soundcards found...
Architecture: i386
ArecordDevices: arecord: device_list:223: no soundcards found...
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer', '/dev/sequencer2', '/dev/sequencer'] failed with exit code 1:
CRDA: Error: [Errno 2] No such file or directory
CurrentDmesg: [ 27.944009] eth0: no IPv6 routers present
Date: Mon May 17 10:11:13 2010
HibernationDevice: RESUME=UUID=e88460fc-5821-40f5-8432-0722907d6bdc
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
MachineType: System Manufacturer System Name
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-22-generic root=UUID=3a460971-de45-41dc-875a-e13aafe4a2fc ro quiet splash
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_GB.UTF-8
RelatedPackageVersions: linux-firmware 1.34
RfKill:

SourcePackage: linux
dmi.bios.date: 04/17/2002
dmi.bios.vendor: Award Software, Inc.
dmi.bios.version: ASUS A7V333 ACPI BIOS Revision 1006
dmi.board.name: A7V333
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: REV 1.xx
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 7
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAwardSoftware,Inc.:bvrASUSA7V333ACPIBIOSRevision1006:bd04/17/2002:svnSystemManufacturer:pnSystemName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnA7V333:rvrREV1.xx:cvnChassisManufacture:ct7:cvrChassisVersion:
dmi.product.name: System Name
dmi.product.version: System Version
dmi.sys.vendor: System Manufacturer