Version:           2.1.0 (using KDE 4.2.90)
OS:                Linux
Installed from:    Fedora RPMs

When closing amarok-2.1, I experienced a crash.
I also saw that crash on 2.0.2/KDE-4.2.4, but this time it looks like it did not crash in xcb but somewhere else:

Application: Amarok (amarok), signal: Segmentation fault
[Current thread is 1 (Thread 0xb7f86780 (LWP 4234))]

Thread 4 (Thread 0xb001cb70 (LWP 4250)):
#0  0x00c39422 in __kernel_vsyscall ()
#1  0x00ce8fa5 in pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S:122
#2  0x04f41257 in QWaitConditionPrivate::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:87
#3  QWaitCondition::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:159
#4  0x00d1a300 in ThreadWeaver::WeaverImpl::blockThreadUntilJobsAreBeingAssigned (this=0x88ba988, th=0x8bfb938) at /usr/src/debug/kdelibs-4.2.90/threadweaver/Weaver/WeaverImpl.cpp:365
#5  0x00d1c97c in ThreadWeaver::WorkingHardState::waitForAvailableJob (this=0x8bf93e0, th=0x8bfb938) at /usr/src/debug/kdelibs-4.2.90/threadweaver/Weaver/WorkingHardState.cpp:80
#6  0x00d189cb in ThreadWeaver::WeaverImpl::waitForAvailableJob (this=0x88ba988, th=0x8bfb938) at /usr/src/debug/kdelibs-4.2.90/threadweaver/Weaver/WeaverImpl.cpp:356
#7  0x00d1ca72 in ThreadWeaver::WorkingHardState::applyForWork (this=0x8bf93e0, th=0x8bfb938) at /usr/src/debug/kdelibs-4.2.90/threadweaver/Weaver/WorkingHardState.cpp:71
#8  0x00d1a583 in ThreadWeaver::WeaverImpl::applyForWork (this=0x88ba988, th=0x8bfb938, previous=0x8b8da60) at /usr/src/debug/kdelibs-4.2.90/threadweaver/Weaver/WeaverImpl.cpp:351
#9  0x00d1ab8e in ThreadWeaver::ThreadRunHelper::run (this=0xb001c284, parent=0x88ba988, th=0x8bfb938) at /usr/src/debug/kdelibs-4.2.90/threadweaver/Weaver/Thread.cpp:87
#10 0x00d1b1ab in ThreadWeaver::Thread::run (this=0x8bfb938) at /usr/src/debug/kdelibs-4.2.90/threadweaver/Weaver/Thread.cpp:142
#11 0x04f4021e in QThreadPrivate::start (arg=0x8bfb938) at thread/qthread_unix.cpp:189
#12 0x00ce4935 in start_thread (arg=0xb001cb70) at pthread_create.c:297
#13 0x0029182e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 3 (Thread 0xaf232b70 (LWP 4255)):
#0  0x00c39422 in __kernel_vsyscall ()
#1  0x00ce92d2 in pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S:179
#2  0x00badcbb in video_decoder_loop (stream_gen=0xa43c6b0) at video_decoder.c:246
#3  0x00ce4935 in start_thread (arg=0xaf232b70) at pthread_create.c:297
#4  0x0029182e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 2 (Thread 0xae664b70 (LWP 4256)):
[KCrash Handler]
#6  0x08803931 in ?? ()
#7  0x00bc069e in post_audio_get_property (port_gen=0x8306008, property=5) at post.c:580
#8  0x00baecc3 in audio_decoder_loop (stream_gen=0xa43c6b0) at audio_decoder.c:133
#9  0x00ce4935 in start_thread (arg=0xae664b70) at pthread_create.c:297
#10 0x0029182e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 1 (Thread 0xb7f86780 (LWP 4234)):
#0  0x00c39422 in __kernel_vsyscall ()
#1  0x00287276 in *__GI___poll (fds=0x320ff4, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:87
#2  0x00d48060 in _xcb_conn_wait (c=0x828a528, cond=0x828b5bc, vector=0xbff71c24, count=0xbff71c28) at xcb_conn.c:306
#3  0x00d485db in _xcb_out_send (c=0x828a528, vector=0xbff71c24, count=0xbff71c28) at xcb_out.c:338
#4  0x00d48977 in xcb_writev (c=0x828a528, vector=0xbff71c78, count=3, requests=31) at xcb_out.c:286
#5  0x005816d9 in _XSend (dpy=0x8287e78, data=0x0, size=0) at xcb_io.c:332
#6  0x00581cb9 in _XFlush (dpy=0x8287e78) at xcb_io.c:349
#7  0x00559b91 in XFlush (dpy=0x8287e78) at Flush.c:41
#8  0x0600f01e in QWidgetPrivate::hide_sys (this=0x82b6688) at kernel/qwidget_x11.cpp:2044
#9  0x05fd4e15 in QWidgetPrivate::hide_helper (this=0x82b6688) at kernel/qwidget.cpp:6804
#10 0x05fdd7f8 in QWidget::setVisible (this=0x82b3ad8, visible=false) at kernel/qwidget.cpp:6984
#11 0x05fd24a6 in QWidget::hide (this=<value optimized out>) at ../../src/gui/kernel/qwidget.h:477
#12 QWidget::~QWidget (this=<value optimized out>) at kernel/qwidget.cpp:1347
#13 0x0600ac85 in QDesktopWidget::~QDesktopWidget (this=0x82b3ad8, __in_chrg=<value optimized out>) at kernel/qdesktopwidget_x11.cpp:228
#14 0x05f8b07c in QApplication::~QApplication (this=0xbff7201c, __in_chrg=<value optimized out>) at kernel/qapplication.cpp:979
#15 0x056e5aca in KApplication::~KApplication (this=0xbff7201c, __in_chrg=<value optimized out>) at /usr/src/debug/kdelibs-4.2.90/kdeui/kernel/kapplication.cpp:893
#16 0x056ecb08 in KUniqueApplication::~KUniqueApplication (this=0xbff7201c, __in_chrg=<value optimized out>) at /usr/src/debug/kdelibs-4.2.90/kdeui/kernel/kuniqueapplication.cpp:371
#17 0x033f62ef in App::~App (this=0xbff7201c, __in_chrg=<value optimized out>) at /usr/src/debug/amarok-2.1/src/App.cpp:281
#18 0x0804c23d in main (argc=1, argv=0xbff72534) at /usr/src/debug/amarok-2.1/src/main.cpp:128