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

Setup is Lenovo T400 in a docking station with two Samsung SyncMaster 2243BWX monitors.
- ATI video card, with open source drivers only (I did not install the proprietary fglrx drivers)

Steps to reproduce:
- Connect both monitors to docking station
- Power up the laptop
- Login screen appears, I log in normally
- Desktop appears but with no panel and no unity launcher
- Although mouse moves, it is unresponsive to clicks and the keyboard does not respond either - only option is a hard reboot.

Workaround:
- Unplug one of the two Samsung monitors
- Reboot
- Log in normally, unity desktop, panels and launcher appear normally
- Plug in the second Samsung monitor, it connects normally and the system is fine

Regression
- This bug appeared after I installed Natty beta 2
- As of yesterday, using the daily build of Apr 13th, I was using the two monitors just fine

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
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: tonyt 1792 F.... pulseaudio
 /dev/snd/controlC0: tonyt 1792 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xfc220000 irq 49'
   Mixer name : 'Conexant CX20561 (Hermosa)'
   Components : 'HDA:14f15051,17aa211c,00100000 HDA:14f12c06,17aa2122,00100000'
   Controls : 16
   Simple ctrls : 8
Card1.Amixer.info:
 Card hw:1 'U0x46d0x809'/'USB Device 0x46d:0x809 at usb-0000:00:1a.7-5.2, high speed'
   Mixer name : 'USB Mixer'
   Components : 'USB046d:0809'
   Controls : 2
   Simple ctrls : 1
Card1.Amixer.values:
 Simple mixer control 'Mic',0
   Capabilities: cvolume cvolume-joined cswitch cswitch-joined penum
   Capture channels: Mono
   Limits: Capture 0 - 17
   Mono: Capture 12 [71%] [23.64dB] [on]
Card29.Amixer.info:
 Card hw:29 'ThinkPadEC'/'ThinkPad Console Audio Control at EC reg 0x30, fw 7VHT16WW-1.06'
   Mixer name : 'ThinkPad EC 7VHT16WW-1.06'
   Components : ''
   Controls : 1
   Simple ctrls : 1
Card29.Amixer.values:
 Simple mixer control 'Console',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Date: Fri Apr 15 08:21:44 2011
Failure: oops
HibernationDevice: RESUME=UUID=d601b148-6ede-4d8b-8758-460ae0cf17e3
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Beta amd64 (20110413.1)
MachineType: LENOVO 2765PCU
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=b5dffa1e-9c41-4ecb-b2dc-e82b1a7613d6 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: No upgrade log present (probably fresh install)
dmi.bios.date: 12/02/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 7VET89WW (3.19 )
dmi.board.name: 2765PCU
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr7VET89WW(3.19):bd12/02/2010:svnLENOVO:pn2765PCU:pvrThinkPadT400:rvnLENOVO:rn2765PCU:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2765PCU
dmi.product.version: ThinkPad T400
dmi.sys.vendor: LENOVO