Unpredictable focusing after switching viewports with the keyboard

Quite frequently after switching viewports with the keyboard, clicking on a window doesn't seemt to focus it properly. Although I can interact with the window in the usual way, it retains the appearance of an unfocused window (eg, the cursor in gnome-terminal remains as the steady, empty rectangle rather than the blinking, solid rectangle. Or selected files in Nautilus don't have the normal highlight colour for a focused window). This didn't seem to happen in Natty, but happens quite randomly in Oneiric.

Focusing another window and then focusing back again seems to correct it.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: compiz 1:0.9.5.92+bzr2791-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-9.14-generic 3.0.3
Uname: Linux 3.0.0-9-generic x86_64
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,compiztoolbox,decor,resize,grid,place,commands,snap,move,mousepoll,imgpng,gnomecompat,session,vpswitch,regex,animation,wall,unitymtgrabhandles,expo,workarounds,fade,scale,ezoom,addhelper,unityshell]
CompositorRunning: compiz
Date: Thu Sep 1 08:23:27 2011
DistUpgraded: Log time: 2010-07-07 18:18:14.820182
DistributionChannelDescriptor: canonical-test
DistroCodename: oneiric
DistroVariant: ubuntu
DpkgLog:

GraphicsCard:
 Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Dell Device [1028:0263]
   Subsystem: Dell Device [1028:0263]
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
MachineType: Dell Inc. Latitude E5500
PackageArchitecture: all
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, user)
 LANG=en_GB.utf8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.0.0-9-generic root=UUID=4ce5e12b-6e82-4fa4-90ff-7d9859d7504e ro quiet splash vt.handoff=7
SourcePackage: compiz
UpgradeStatus: Upgraded to oneiric on 2010-07-07 (420 days ago)
dmi.bios.date: 11/05/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A15
dmi.board.name: 0DW635
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA15:bd11/05/2009:svnDellInc.:pnLatitudeE5500:pvr:rvnDellInc.:rn0DW635:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Latitude E5500
dmi.sys.vendor: Dell Inc.
version.compiz: compiz 1:0.9.5.92+bzr2791-0ubuntu1
version.ia32-libs: ia32-libs 20090808ubuntu19
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+7ubuntu6
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