compiz crashed with SIGSEGV in sigc::signal_base::impl()

[hellojoker]

Binary package hint: unity

Unity crashed when I enabled motion blur in compizconfig Settings Manager

It also happens with the activation of other effects.

Unity when it is restarted some effects work

Window Previews works when windows are open?!?

ProblemType: Crash
DistroRelease: Ubuntu 11.04
Package: unity 3.4.6-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-5.32-generic 2.6.38-rc6
Uname: Linux 2.6.38-5-generic x86_64
Architecture: amd64
CrashCounter: 1
Date: Sat Feb 26 01:52:56 2011
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/compiz
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20110223)
ProcCmdline: compiz
ProcEnviron:
 LANGUAGE=it_IT:en
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SegvAnalysis:
 Segfault happened at: 0x7f37699e12f6 <_ZNK4sigc11signal_base4implEv+22>: mov 0x8(%rdi),%rbx
 PC (0x7f37699e12f6) ok
 source "0x8(%rdi)" (0x000000e8) not located in a known VMA region (needed readable region)!
 destination "%rbx" ok
SegvReason: reading NULL VMA
Signal: 11
SourcePackage: unity
StacktraceTop:
 sigc::signal_base::impl() const () from /usr/lib/libsigc-2.0.so.0
 sigc::signal_base::connect(sigc::slot_base const&) () from /usr/lib/libsigc-2.0.so.0
 UnityScreen::UnityScreen(CompScreen*) () from /usr/lib/compiz/libunityshell.so
 CompPlugin::VTableForScreenAndWindow<UnityScreen, UnityWindow>::initScreen(CompScreen*) () from /usr/lib/compiz/libunityshell.so
 CompManager::initPlugin(CompPlugin*) ()
Title: compiz crashed with SIGSEGV in sigc::signal_base::impl()
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare

[Apport retracing service (apport)]

Thank you for taking the time to report this crash and helping to make Ubuntu better. This particular crash has already been reported and is a duplicate of bug #725282, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.