WARNING: at /build/buildd/linux-2.6.38/ubuntu/aufs/plink.c:450 au_plink_put+0x4c/0xa0 [aufs]()

I have no idea what was caused this. I wasn't doing anything in particular.

ProblemType: KernelOops
DistroRelease: Ubuntu 11.04
Package: linux-image-2.6.38-8-generic 2.6.38-8.41
Regression: Yes
Reproducible: No
ProcVersionSignature: Ubuntu 2.6.38-8.41-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
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: barry 2853 F.... pulseaudio
 /dev/snd/controlC1: barry 2853 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xfbcf8000 irq 44'
   Mixer name : 'Realtek ALC1200'
   Components : 'HDA:10ec0888,102802c9,00100101'
   Controls : 37
   Simple ctrls : 20
Card1.Amixer.info:
 Card hw:1 'Headset'/'Logitech Logitech USB Headset at usb-0000:00:1a.2-1, full speed'
   Mixer name : 'USB Mixer'
   Components : 'USB046d:0a01'
   Controls : 6
   Simple ctrls : 2
Card2.Amixer.info:
 Card hw:2 'HDMI'/'HDA ATI HDMI at 0xfbefc000 irq 45'
   Mixer name : 'ATI R6xx HDMI'
   Components : 'HDA:1002aa01,00aa0100,00100100'
   Controls : 4
   Simple ctrls : 1
Card2.Amixer.values:
 Simple mixer control 'IEC958',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Date: Thu Apr 7 13:25:52 2011
Failure: oops
Frequency: This has only happened once.
HibernationDevice: RESUME=UUID=bfeef982-28a1-4817-b4cb-5abfe261219a
MachineType: Dell Inc. Studio XPS 435MT
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=62a2a88d-479b-42ae-b74f-3fd7870652fd 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
RfKill:

SourcePackage: linux
Title: WARNING: at /build/buildd/linux-2.6.38/ubuntu/aufs/plink.c:450 au_plink_put+0x4c/0xa0 [aufs]()
UpgradeStatus: Upgraded to natty on 2011-04-05 (2 days ago)
dmi.bios.date: 05/05/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.1.1
dmi.board.name: 0R849J
dmi.board.vendor: Dell Inc.
dmi.board.version: A03
dmi.chassis.type: 3
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.1.1:bd05/05/2009:svnDellInc.:pnStudioXPS435MT:pvr:rvnDellInc.:rn0R849J:rvrA03:cvnDellInc.:ct3:cvr:
dmi.product.name: Studio XPS 435MT
dmi.sys.vendor: Dell Inc.