Application spread view (Compiz scale) doesn't work properly after using "Show Desktop"

What steps will reproduce the problem?

1. Open two or more windows of an application like Nautilus so that all are visible on the screen
2. Use the "Show Desktop" button to hide the windows
3. Activate the window spread by clicking at the icon of the application you launched two times

What is the expected output?

- all windows of the application (from current workspace) are shown in the spread, represented by a thumbnail

What do you see instead?

- all windows are technically "shown" but only the window activated by the first click at the icon has a working thumbnail
- the area where the other window-thumbnails should be located is functional but the thumbnails are missing

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: unity 6.12.0daily13.01.21-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-1.5-generic 3.8.0-rc4
Uname: Linux 3.8.0-1-generic x86_64
NonfreeKernelModules: nvidia
.proc.driver.nvidia.gpus.0: Error: [Errno 21] Ist ein Verzeichnis: '/proc/driver/nvidia/gpus/0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 310.19 Thu Nov 8 00:52:03 PST 2012
 GCC version: gcc-Version 4.7.2 (Ubuntu/Linaro 4.7.2-19ubuntu1)
.proc.driver.nvidia.warnings.fbdev:
 Your system is not currently configured to drive a VGA console
 on the primary VGA device. The NVIDIA Linux graphics driver
 requires the use of a text-mode VGA console. Use of other console
 drivers including, but not limited to, vesafb, may result in
 corruption and stability problems, and is not supported.
.tmp.unity.support.test.0:

ApportVersion: 2.8-0ubuntu2
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
Date: Fri Jan 25 02:19:52 2013
DistUpgraded: Fresh install
DistroCodename: raring
DistroVariant: ubuntu
DkmsStatus: nvidia-310, 310.19, 3.8.0-1-generic, x86_64: installed
GraphicsCard:
 NVIDIA Corporation GF114 [GeForce GTX 560 Ti] [10de:1200] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. Device [1043:8390]
InstallationDate: Installed on 2013-01-22 (2 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130122)
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-1-generic root=UUID=db108b5c-1f1d-4fe4-99bd-234f619ae6cf ro quiet splash nomodeset video=uvesafb:mode_option=1280x1024-24,mtrr=3,scroll=ywrap vt.handoff=7
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/11/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P2.20
dmi.board.name: P67 Extreme4 Gen3
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.:bvrP2.20:bd05/11/2012:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnP67Extreme4Gen3: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 1:0.9.9~daily13.01.21-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.41-0ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 9.0.1-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.0.1-0ubuntu1
version.nvidia-graphics-drivers: nvidia-graphics-drivers N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.13.1.901-0ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.0.0-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.20.19-0ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.6-0ubuntu1
xserver.bootTime: Thu Jan 24 15:13:16 2013
xserver.configfile: default
xserver.errors:
 open /dev/dri/card0: No such file or directory
 open /dev/dri/card0: No such file or directory
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:

xserver.version: 2:1.13.1.901-0ubuntu2