Lock screen sometimes doesn't clear the external monitor

[Walter Ribeiro]

Steps to reproduce:

1. Plug an external monitor and configure twin view.
2. Move a Window (anyone) to second monitor
3. Open a Window in main monitor (keep focus on it)
4. Leave the mouse stationary, pointing to screen 1, don't move it.
5. Quickly press Ctrl-Alt-L
6. The screen in main monitor becomes black and occasionally the other continues showing the image.

Moving the mouse, or pressing any key, the image in second screen disappear.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: compiz 1:0.9.9~daily13.03.08-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-12.21-generic 3.8.2
Uname: Linux 3.8.0-12-generic i686
NonfreeKernelModules: wl nvidia
.proc.driver.nvidia.gpus.0: Error: [Errno 21] É um diretório: '/proc/driver/nvidia/gpus/0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86 Kernel Module 304.84 Wed Feb 27 05:03:32 PST 2013
 GCC version: versão do gcc 4.7.2 (Ubuntu/Linaro 4.7.2-22ubuntu3)
.tmp.unity.support.test.0:

ApportVersion: 2.9.1-0ubuntu1
Architecture: i386
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
Date: Wed Mar 13 17:00:27 2013
DistUpgraded: Fresh install
DistroCodename: raring
DistroVariant: ubuntu
GraphicsCard:
 NVIDIA Corporation C67 [GeForce 7150M / nForce 630M] [10de:0531] (rev a2) (prog-if 00 [VGA controller])
   Subsystem: Hewlett-Packard Company Device [103c:30cf]
InstallationDate: Installed on 2013-02-17 (24 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha i386 (20130208)
MachineType: Hewlett-Packard HP Pavilion dv6500 Notebook PC
MarkForUpload: True
PackageArchitecture: all
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-12-generic root=UUID=3f5dba1f-191b-4bd6-a67a-f2d031435939 ro quiet splash
SourcePackage: compiz
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/22/2011
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: F.34
dmi.board.name: 30CF
dmi.board.vendor: Quanta
dmi.board.version: 85.26
dmi.chassis.type: 10
dmi.chassis.vendor: Quanta
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnHewlett-Packard:bvrF.34:bd03/22/2011:svnHewlett-Packard:pnHPPaviliondv6500NotebookPC:pvrRev1:rvnQuanta:rn30CF:rvr85.26:cvnQuanta:ct10:cvrN/A:
dmi.product.name: HP Pavilion dv6500 Notebook PC
dmi.product.version: Rev 1
dmi.sys.vendor: Hewlett-Packard
version.compiz: compiz 1:0.9.9~daily13.03.08-0ubuntu1
version.libdrm2: libdrm2 2.4.42-0ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 9.0.2-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.0.2-0ubuntu1
version.nvidia-graphics-drivers: nvidia-graphics-drivers N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.13.2-0ubuntu3
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.1.0-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.21.4-0ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.6-0ubuntu3
xserver.bootTime: Wed Mar 13 14:03:27 2013
xserver.configfile: default
xserver.errors:
 open /dev/dri/card0: No such file or directory
 open /dev/dri/card0: No such file or directory
 open /dev/fb0: No such file or directory
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:

xserver.version: 2:1.13.2-0ubuntu3

[Launchpad Janitor (janitor)]

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