Application: kwin (4.4.00 (KDE 4.4.0))
KDE Platform Version: 4.4.00 (KDE 4.4.0)
Qt Version: 4.6.1
Operating System: Linux 2.6.31-19-generic x86_64
Distribution: Ubuntu 9.10

-- Information about the crash:
I had just clicked on the taskbar button for a running app that I believe was on the already active desktop when things went a little funky (The newly active window went dark for a sec, I have the dim-background-windows plugin on, so it may have been a popup I didn't catch sight of) and then I noticed the window decorations vanishing and reapearing (with different colors) and the DrKonqi pop-up appeared with them.

 -- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
The current source language is "auto; currently c".
[Current thread is 1 (Thread 0x7f0ab0750820 (LWP 2944))]

Thread 2 (Thread 0x7f0a91ca2910 (LWP 2945)):
#0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:97
#1  0x00007f0ab009fb11 in _L_lock_9274 () from /lib/libc.so.6
#2  0x00007f0ab009d741 in *__GI___libc_free (mem=0x7f0ab038de40) at malloc.c:3714
#3  0x00007f0aac0298d1 in socketNotifierSourceCheck (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:92
#4  0x00007f0aa4b61aaa in g_main_context_check () from /lib/libglib-2.0.so.0
#5  0x00007f0aa4b62290 in ?? () from /lib/libglib-2.0.so.0
#6  0x00007f0aa4b626c0 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#7  0x00007f0aac029463 in QEventDispatcherGlib::processEvents (this=0x21bcfc0, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:412
#8  0x00007f0aabffe862 in QEventLoop::processEvents (this=<value optimized out>, flags=) at kernel/qeventloop.cpp:149
#9  0x00007f0aabffec3c in QEventLoop::exec (this=0x7f0a91ca1f30, flags=) at kernel/qeventloop.cpp:201
#10 0x00007f0aabf08d29 in QThread::exec (this=<value optimized out>) at thread/qthread.cpp:487
#11 0x00007f0aabfdf098 in QInotifyFileSystemWatcherEngine::run (this=0x21b4000) at io/qfilesystemwatcher_inotify.cpp:248
#12 0x00007f0aabf0b745 in QThreadPrivate::start (arg=0x21b4000) at thread/qthread_unix.cpp:248
#13 0x00007f0aabc7ca04 in start_thread (arg=<value optimized out>) at pthread_create.c:300
#14 0x00007f0ab010280d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#15 0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f0ab0750820 (LWP 2944)):
[KCrash Handler]
#5  0x00007f0ab0098e5d in malloc_consolidate (av=0x7f0ab038de40) at malloc.c:5103
#6  0x00007f0ab009b509 in _int_malloc (av=0x7f0ab038de40, bytes=0) at malloc.c:4338
#7  0x00007f0ab009d82e in *__GI___libc_malloc (bytes=2884) at malloc.c:3638
#8  0x00007f0aa78f1fbe in ?? () from /usr/lib/libxcb.so.1
#9  0x00007f0aa78f032d in ?? () from /usr/lib/libxcb.so.1
#10 0x00007f0aa78f1c2c in xcb_wait_for_reply () from /usr/lib/libxcb.so.1
#11 0x00007f0aae544f23 in _XReply (dpy=0x214cc80, rep=0x7fff76c17bb0, extra=0, discard=0) at ../../src/xcb_io.c:454
#12 0x00007f0aae5331fd in XQueryTree (dpy=0x214cc80, w=340, root=0x7fff76c17c70, parent=0x7fff76c17c70, children=0x7fff76c17c68, nchildren=0x7fff76c17c7c) at ../../src/QuTree.c:49
#13 0x00007f0ab03dcc19 in KWin::Workspace::xStackingOrder (this=0x2223d30) at ../../kwin/layers.cpp:763
#14 0x00007f0ab043daab in KWin::Workspace::performCompositing (this=<value optimized out>) at ../../kwin/composite.cpp:390
#15 0x00007f0ab03c7dee in KWin::Workspace::qt_metacall (this=0x2223d30, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fff76c17f40) at ./workspace.moc:535
#16 0x00007f0aac012d3f in QMetaObject::activate (sender=0x22241a0, m=<value optimized out>, local_signal_index=<value optimized out>, argv=0x7f0ab038de48) at kernel/qobject.cpp:3275
#17 0x00007f0aac00f993 in QObject::event (this=0x22241a0, e=0x7fff76c18690) at kernel/qobject.cpp:1212
#18 0x00007f0aac74dfac in QApplicationPrivate::notify_helper (this=0x2125420, receiver=0x22241a0, e=0x7fff76c18690) at kernel/qapplication.cpp:4298
#19 0x00007f0aac75459b in QApplication::notify (this=0x7fff76c189f0, receiver=0x22241a0, e=0x7fff76c18690) at kernel/qapplication.cpp:4181
#20 0x00007f0aafc0cd16 in KApplication::notify (this=0x7fff76c189f0, receiver=0x22241a0, event=0x7fff76c18690) at ../../kdeui/kernel/kapplication.cpp:302
#21 0x00007f0aabffff3c in QCoreApplication::notifyInternal (this=0x7fff76c189f0, receiver=0x22241a0, event=0x7fff76c18690) at kernel/qcoreapplication.cpp:704
#22 0x00007f0aac02cb92 in QCoreApplication::sendEvent (this=0x21290c0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#23 QTimerInfoList::activateTimers (this=0x21290c0) at kernel/qeventdispatcher_unix.cpp:603
#24 0x00007f0aac029798 in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:184
#25 idleTimerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:231
#26 0x00007f0aa4b5ebce in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#27 0x00007f0aa4b62598 in ?? () from /lib/libglib-2.0.so.0
#28 0x00007f0aa4b626c0 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#29 0x00007f0aac029463 in QEventDispatcherGlib::processEvents (this=0x210bf30, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:412
#30 0x00007f0aac7fd7ee in QGuiEventDispatcherGlib::processEvents (this=0x7f0ab038de40, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:204
#31 0x00007f0aabffe862 in QEventLoop::processEvents (this=<value optimized out>, flags=) at kernel/qeventloop.cpp:149
#32 0x00007f0aabffec3c in QEventLoop::exec (this=0x7fff76c18930, flags=) at kernel/qeventloop.cpp:201
#33 0x00007f0aac00297b in QCoreApplication::exec () at kernel/qcoreapplication.cpp:981
#34 0x00007f0ab03e15ae in kdemain (argc=<value optimized out>, argv=<value optimized out>) at ../../kwin/main.cpp:526
#35 0x00007f0ab0041abd in __libc_start_main (main=<value optimized out>, argc=<value optimized out>, ubp_av=<value optimized out>, init=<value optimized out>, fini=<value optimized out>, 
    rtld_fini=<value optimized out>, stack_end=0x7fff76c18ef8) at libc-start.c:220
#36 0x0000000000400679 in _start () at ../sysdeps/x86_64/elf/start.S:113
The current source language is "auto; currently asm".
The current source language is "auto; currently c".

Reported using DrKonqi