unlock screen sticks

When unlocking the desktop screen, it just sits there with a black background and a white mouse pointer. If I switch to a virtual terminal I can see that Compiz is pegging my CPU. I kill it with -9 and switch back and the screen is back to normal.
It has always been slow to paint the desktop after unlocking, but recently it has been consistent.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: compiz 1:0.9.7.12-0ubuntu2
ProcVersionSignature: Ubuntu 3.2.0-52.78-generic 3.2.48
Uname: Linux 3.2.0-52-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.0.1-0ubuntu17.4
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
CompositorRunning: compiz
Date: Wed Aug 28 13:58:53 2013
DistUpgraded: Fresh install
DistroCodename: precise
DistroVariant: ubuntu
GraphicsCard:
 Advanced Micro Devices [AMD] nee ATI RV620 LE [Radeon HD 3450] [1002:95c5] (prog-if 00 [VGA controller])
   Subsystem: Dell Device [1028:0342]
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120822.4)
MachineType: Dell Inc. OptiPlex 960
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-52-generic root=UUID=138260dc-ec89-47b0-9c8c-42bfefa99f7d ro quiet splash vt.handoff=7
SourcePackage: compiz
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/03/2010
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A08
dmi.board.name: 0Y958C
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 6
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA08:bd08/03/2010:svnDellInc.:pnOptiPlex960:pvr:rvnDellInc.:rn0Y958C:rvrA00:cvnDellInc.:ct6:cvr:
dmi.product.name: OptiPlex 960
dmi.sys.vendor: Dell Inc.
version.compiz: compiz 1:0.9.7.12-0ubuntu2
version.ia32-libs: ia32-libs 20090808ubuntu36
version.libdrm2: libdrm2 2.4.43-0ubuntu0.0.2
version.libgl1-mesa-dri: libgl1-mesa-dri 8.0.4-0ubuntu0.6
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 8.0.4-0ubuntu0.6
version.xserver-xorg-core: xserver-xorg-core 2:1.11.4-0ubuntu10.13
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.0-0ubuntu1.2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20111219.aacbd629-0ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.17.0-1ubuntu4.4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20111201+b5534a1-1build3