compiz crashed with SIGSEGV in pthread_mutex_lock()

Binary package hint: compiz

hard crash while summoning a lens with a kb shortcut

ProblemType: Crash
DistroRelease: Ubuntu 11.04
Package: compiz-core 1:0.9.4+bzr20110407-0ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-8.41-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
NonfreeKernelModules: nvidia
.proc.driver.nvidia.gpus.0: Error: [Errno 21] Is a directory: '/proc/driver/nvidia/gpus/0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 270.30 Fri Feb 25 14:34:55 PST 2011
 GCC version: gcc version 4.5.2 (Ubuntu/Linaro 4.5.2-8ubuntu1)
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,decor,mousepoll,vpswitch,regex,animation,snap,expo,move,compiztoolbox,place,grid,imgpng,gnomecompat,wall,ezoom,workarounds,staticswitcher,resize,fade,unitymtgrabhandles,scale,session,unityshell]
CompositorRunning: compiz
Date: Sat Apr 9 17:30:09 2011
DistUpgraded: Fresh install
DistroCodename: natty
DistroVariant: ubuntu
DkmsStatus: nvidia-current, 270.30, 2.6.38-8-generic, x86_64: installed
ExecutablePath: /usr/bin/compiz
GraphicsCard:
 nVidia Corporation G86 [GeForce 9400 GT] [10de:042c] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: Device [196e:0561]
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Beta amd64 (20110407.1)
InstallationMedia_: Ubuntu 11.04 "Natty Narwhal" - Beta amd64 (20110407.1)
JockeyStatus: xorg:nvidia_current - NVIDIA accelerated graphics driver (Proprietary, Enabled, In use)
MachineType: Acer Aspire M3400
ProcCmdline: compiz
ProcEnviron:
 LANGUAGE=en_US:en
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=be008253-26d5-43d3-9ff2-f22b84f00f7a ro quiet splash vt.handoff=7
ProcVersionSignature_: Ubuntu 2.6.38-8.41-generic 2.6.38.2
Renderer: Unknown
SegvAnalysis:
 Segfault happened at: 0x7f32fd96d394 <pthread_mutex_lock+4>: mov 0x10(%rdi),%esi
 PC (0x7f32fd96d394) ok
 source "0x10(%rdi)" (0xfff854c0e8c78960) not located in a known VMA region (needed readable region)!
 destination "%esi" ok
SegvReason: reading unknown VMA
Signal: 11
SourcePackage: compiz
StacktraceTop:
 pthread_mutex_lock () from /lib/x86_64-linux-gnu/libpthread.so.0
 ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
 PrivateScreen::~PrivateScreen() ()
 PrivateScreen::~PrivateScreen() ()
 CompScreen::~CompScreen() ()
Title: compiz crashed with SIGSEGV in pthread_mutex_lock()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
dmi.bios.date: 04/21/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P01-A2
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: Aspire M3400
dmi.board.vendor: Acer
dmi.chassis.type: 3
dmi.chassis.vendor: Acer
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP01-A2:bd04/21/2010:svnAcer:pnAspireM3400:pvr:rvnAcer:rnAspireM3400:rvr:cvnAcer:ct3:cvr:
dmi.product.name: Aspire M3400
dmi.sys.vendor: Acer
version.compiz: compiz 1:0.9.4+bzr20110407-0ubuntu2
version.ia32-libs: ia32-libs 20090808ubuntu11
version.libdrm2: libdrm2 2.4.23-1ubuntu6
version.libgl1-mesa-dri: libgl1-mesa-dri 7.10.1-0ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 7.10.1-0ubuntu3
version.nvidia-graphics-drivers: nvidia-graphics-drivers N/A
version.xserver-xorg: xserver-xorg 1:7.6+4ubuntu3
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.0-0ubuntu4
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.14.0-4ubuntu6
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110107+b795ca6e-0ubuntu6