Desktop has offset (black bars on the left and top)

[iGadget]

After today's updates, my desktop suddenly looks as shown in the attached screenshot. When switching desktops, parts of the first desktop are 'left behind' in the black areas, as shown in the second screenshot.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: unity 4.20.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-12.19-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 1.23-0ubuntu2
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,compiztoolbox,decor,regex,resize,move,mousepoll,snap,grid,gnomecompat,place,animation,vpswitch,imgpng,unitymtgrabhandles,session,wall,expo,workarounds,ezoom,fade,scale,unityshell]
CompositorRunning: compiz
Date: Fri Sep 30 08:24:48 2011
DistUpgraded: Log time: 2011-09-02 00:03:39.716433
DistroCodename: oneiric
DistroVariant: ubuntu
GraphicsCard:
 Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0102] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: ASRock Incorporation Device [1849:0102]
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Alpha amd64 (20110803.1)
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.0.0-12-generic root=UUID=24ee2295-58ad-4d06-a4eb-c0c7359e2bb6 ro quiet splash vt.handoff=7
SourcePackage: unity
UpgradeStatus: Upgraded to oneiric on 2011-09-28 (2 days ago)
dmi.bios.date: 01/17/2011
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P1.30
dmi.board.name: H67M-GE
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP1.30:bd01/17/2011:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnH67M-GE:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.
version.compiz: compiz 1:0.9.6+bzr20110929-0ubuntu1
version.ia32-libs: ia32-libs 20090808ubuntu25
version.libdrm2: libdrm2 2.4.26-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 7.11-0ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 7.11-0ubuntu3
version.xserver-xorg: xserver-xorg 1:7.6+7ubuntu7
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.6.0-1ubuntu13
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20110811.g93fc084-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.15.901-1ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110411+8378443-1

[iGadget (igadget)]

And here's the second screenshot.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.