Comment 18 for bug 685682

Felix points out this is being caused by compiz crashing. So it appears not to be an X or fglrx bug but rather something in nux:

Backtrace:
#0 0x0000000000000000 in ?? ()
#1 0x00007fffeb58fcf0 in nux::IOpenGLSurface::UnlockRect() ()
   from /usr/lib/libnux-graphics-0.9.so.0
#2 0x00007fffeb58798a in nux::IOpenGLTexture2D::UnlockRect(int) ()
   from /usr/lib/libnux-graphics-0.9.so.0
#3 0x00007fffeb55a545 in nux::CachedTexture2D::LoadMipLevel(nux::BaseTexture*, int) () from
/usr/lib/libnux-graphics-0.9.so.0
#4 0x00007fffeb55ae2d in nux::CachedTexture2D::CachedTexture2D(nux::NResourceSet*, nux::Texture2D*) () from
/usr/lib/libnux-graphics-0.9.so.0
#5 0x00007fffeb557b54 in nux::TGLResourceFactory<nux::Texture2D,
nux::CachedTexture2D>::BuildResource(nux::NResourceSet*, nux::ResourceData*) ()
   from /usr/lib/libnux-graphics-0.9.so.0
#6 0x00007fffeb55736c in nux::NResourceCache::GetCachedResource(nux::ResourceData*) () from
/usr/lib/libnux-graphics-0.9.so.0
#7 0x00007fffeb54c8cd in nux::GraphicsEngine::CacheResource(nux::ResourceData*) () from
/usr/lib/libnux-graphics-0.9.so.0
#8 0x00007fffeb55a09f in nux::BaseTexture::GetDeviceTexture() ()
   from /usr/lib/libnux-graphics-0.9.so.0
#9 0x00007fffebbbdfa1 in PanelHomeButton::Refresh() ()
   from /usr/lib/compiz/libunityshell.so
#10 0x00007fffebbbe371 in PanelHomeButton::PanelHomeButton() ()
   from /usr/lib/compiz/libunityshell.so
#11 0x00007fffebbc4b96 in PanelView::PanelView(char const*, int) ()
   from /usr/lib/compiz/libunityshell.so
#12 0x00007fffebbde85c in UnityScreen::initLauncher(nux::NThread*, void*) ()
   from /usr/lib/compiz/libunityshell.so
#13 0x00007fffebbdeabd in UnityScreen::initUnity(nux::NThread*, void*) ()
   from /usr/lib/compiz/libunityshell.so
#14 0x00007fffeb919282 in nux::WindowThread::Run(void*) ()
   from /usr/lib/libnux-0.9.so.0
#15 0x00007fffebbdf57a in UnityScreen::UnityScreen(CompScreen*) ()
   from /usr/lib/compiz/libunityshell.so
#16 0x00007fffebbe1c49 in CompPlugin::VTableForScreenAndWindow<UnityScreen, UnityWindow>::initScreen(CompScreen*)
() from /usr/lib/compiz/libunityshell.so
#17 0x00000000004501fa in CompManager::initPlugin(CompPlugin*) ()
#18 0x00000000004512fe in CompPlugin::push(CompPlugin*) ()
#19 0x000000000042d588 in PrivateScreen::updatePlugins() ()
#20 0x000000000042d898 in PrivateScreen::processEvents() ()
#21 0x000000000042d8f8 in CompEventSource::callback() ()
#22 0x00007ffff6e4440f in Glib::Source::dispatch_vfunc(_GSource*, int (*)(void*), void*) () from
/usr/lib/libglibmm-2.4.so.1
#23 0x00007ffff6956c4d in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#24 0x00007ffff6957438 in ?? () from /lib/libglib-2.0.so.0
#25 0x00007ffff69576c9 in g_main_context_iteration ()
   from /lib/libglib-2.0.so.0
#26 0x00007ffff6e452e3 in Glib::MainContext::iteration(bool) ()
   from /usr/lib/libglibmm-2.4.so.1
#27 0x000000000042932a in CompScreen::eventLoop() ()
#28 0x00000000004222e0 in main ()