WARNING: at /build/buildd/linux-2.6.38/drivers/gpu/drm/radeon/radeon_fence.c:248 radeon_fence_wait+0x36f/0x3e0 [radeon]()

I do not understand

ProblemType: KernelOops
DistroRelease: Ubuntu 11.04
Package: linux-image-2.6.38-8-generic 2.6.38-8.42
Regression: Yes
Reproducible: Yes
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Annotation: Your system might become unstable now and might need to be restarted.
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC271X Analog [ALC271X Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: sinxwal 5005 F.... pulseaudio
 /dev/snd/pcmC0D0p: sinxwal 5005 F...m pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xcc100000 irq 42'
   Mixer name : 'Realtek ALC271X'
   Components : 'HDA:10ec0269,10250359,00100100'
   Controls : 18
   Simple ctrls : 10
Card1.Amixer.info:
 Card hw:1 'Generic'/'HD-Audio Generic at 0xcc020000 irq 43'
   Mixer name : 'ATI R6xx HDMI'
   Components : 'HDA:1002aa01,00aa0100,00100200'
   Controls : 4
   Simple ctrls : 1
Card1.Amixer.values:
 Simple mixer control 'IEC958',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Date: Sat Apr 16 11:38:54 2011
Failure: oops
HibernationDevice: RESUME=UUID=167ac524-4c24-476e-92eb-e39e795027aa
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
Lsusb:
 Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 001 Device 003: ID 0402:9665 ALi Corp.
 Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Acer Aspire 4820TG
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=366f962b-c505-48c5-8fa5-56bdc87d5154 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-2.6.38-8-generic N/A
 linux-backports-modules-2.6.38-8-generic N/A
 linux-firmware 1.50
SourcePackage: linux
Title: WARNING: at /build/buildd/linux-2.6.38/drivers/gpu/drm/radeon/radeon_fence.c:248 radeon_fence_wait+0x36f/0x3e0 [radeon]()
UpgradeStatus: Upgraded to natty on 2011-04-05 (10 days ago)
dmi.bios.date: 09/08/2010
dmi.bios.vendor: INSYDE
dmi.bios.version: V1.19
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: ZQ1B
dmi.board.vendor: Acer
dmi.board.version: Base Board Version
dmi.chassis.type: 10
dmi.chassis.vendor: Chassis Manufacturer
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnINSYDE:bvrV1.19:bd09/08/2010:svnAcer:pnAspire4820TG:pvrV1.19:rvnAcer:rnZQ1B:rvrBaseBoardVersion:cvnChassisManufacturer:ct10:cvrChassisVersion:
dmi.product.name: Aspire 4820TG
dmi.product.version: V1.19
dmi.sys.vendor: Acer