Application that crashed: kontact
Version of the application: 4.3.1
KDE Version: 4.3.1 (KDE 4.3.1)
Qt Version: 4.5.2
Operating System: Linux 2.6.30.5-43.fc11.x86_64 x86_64

What I was doing when the application crashed:
I managed to reproduce the error a couple of times (although not every time). 
I am not sure this is relevant, but in the occasions when it crashed I had a mailbox opened and pressed Ctrl-q or used the menu to close the application; I tried a couple of times having opened something else - the Summary, Contacts or Calendar, but it didn't crash then.

 -- Backtrace:
Application: Kontact (kontact), signal: Segmentation fault
[Current thread is 1 (Thread 0x7f953e6da820 (LWP 22548))]

Thread 3 (Thread 0x7f9529e94910 (LWP 22552)):
#0  0x0000003523a0b57d in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x0000003f9145ad62 in QWaitConditionPrivate::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:85
#2  QWaitCondition::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:159
#3  0x0000003f91450e3a in QThreadPoolThread::run (this=<value optimized out>) at concurrent/qthreadpool.cpp:140
#4  0x0000003f91459d45 in QThreadPrivate::start (arg=0x2720f70) at thread/qthread_unix.cpp:188
#5  0x0000003523a0686a in start_thread () from /lib64/libpthread.so.0
#6  0x0000003522ede3bd in clone () from /lib64/libc.so.6
#7  0x0000000000000000 in ?? ()

Thread 2 (Thread 0x7f9529266910 (LWP 22556)):
#0  0x0000003523a0b57d in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x0000003f9145ad62 in QWaitConditionPrivate::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:85
#2  QWaitCondition::wait (time=<value optimized out>, this=<value optimized out>) at thread/qwaitcondition_unix.cpp:159
#3  0x0000003f91450e3a in QThreadPoolThread::run (this=<value optimized out>) at concurrent/qthreadpool.cpp:140
#4  0x0000003f91459d45 in QThreadPrivate::start (arg=0x273ee80) at thread/qthread_unix.cpp:188
#5  0x0000003523a0686a in start_thread () from /lib64/libpthread.so.0
#6  0x0000003522ede3bd in clone () from /lib64/libc.so.6
#7  0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f953e6da820 (LWP 22548)):
[KCrash Handler]
#5  QBasicAtomicInt::operator!= (value=<value optimized out>, this=<value optimized out>) at /usr/include/QtCore/qbasicatomic.h:69
#6  QMap<KJob*, KMail::ImapAccountBase::jobData>::detach (value=<value optimized out>, this=<value optimized out>) at /usr/include/QtCore/qmap.h:172
#7  QMap<KJob*, KMail::ImapAccountBase::jobData>::find (value=<value optimized out>, this=<value optimized out>) at /usr/include/QtCore/qmap.h:565
#8  KMail::ImapAccountBase::findJob (value=<value optimized out>, this=<value optimized out>) at /usr/src/debug/kdepim-4.3.1/kmail/imapaccountbase.h:180
#9  KMail::ListJob::slotListEntries (value=<value optimized out>, this=<value optimized out>) at /usr/src/debug/kdepim-4.3.1/kmail/listjob.cpp:189
#10 0x00007f9530fa1d77 in KMail::ListJob::qt_metacall (this=0x29cfe00, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fff8ed6ab40)
    at /usr/src/debug/kdepim-4.3.1/x86_64-redhat-linux-gnu/kmail/listjob.moc:78
#11 0x0000003f915547dc in QMetaObject::activate (sender=0x29d0590, from_signal_index=<value optimized out>, to_signal_index=<value optimized out>, argv=0x7fff8ed6ab38) at kernel/qobject.cpp:3113
#12 0x000000325cae6f34 in KIO::ListJob::entries (this=0x29cfe00, _t1=0x29d0590, _t2=<value optimized out>) at /usr/src/debug/kdelibs-4.3.1/x86_64-redhat-linux-gnu/kio/jobclasses.moc:781
#13 0x000000325caf55f7 in KIO::ListJobPrivate::slotListEntries (this=0x29d0730, list=<value optimized out>) at /usr/src/debug/kdelibs-4.3.1/kio/kio/job.cpp:2333
#14 0x000000325caf598a in KIO::ListJob::qt_metacall (this=0x29d0590, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fff8ed6aec0)
    at /usr/src/debug/kdelibs-4.3.1/x86_64-redhat-linux-gnu/kio/jobclasses.moc:767
#15 0x0000003f915547dc in QMetaObject::activate (sender=0x2731c80, from_signal_index=<value optimized out>, to_signal_index=<value optimized out>, argv=0x7fff8ed6ab38) at kernel/qobject.cpp:3113
#16 0x000000325cbac5d5 in KIO::SlaveInterface::listEntries (this=0x29cfe00, _t1=<value optimized out>) at /usr/src/debug/kdelibs-4.3.1/x86_64-redhat-linux-gnu/kio/slaveinterface.moc:179
#17 0x000000325cbb002d in KIO::SlaveInterface::dispatch (this=0x2731c80, _cmd=<value optimized out>, rawdata=@0x7fff8ed6b0e0) at /usr/src/debug/kdelibs-4.3.1/kio/kio/slaveinterface.cpp:193
#18 0x000000325cbac9b3 in KIO::SlaveInterface::dispatch (this=0x2731c80) at /usr/src/debug/kdelibs-4.3.1/kio/kio/slaveinterface.cpp:91
#19 0x000000325cb9f7ed in KIO::Slave::gotInput (this=0x2731c80) at /usr/src/debug/kdelibs-4.3.1/kio/kio/slave.cpp:322
#20 0x000000325cba18fc in KIO::Slave::qt_metacall (this=0x2731c80, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fff8ed6b250)
    at /usr/src/debug/kdelibs-4.3.1/x86_64-redhat-linux-gnu/kio/slave.moc:76
#21 0x0000003f915547dc in QMetaObject::activate (sender=0x27317c0, from_signal_index=<value optimized out>, to_signal_index=<value optimized out>, argv=0x7fff8ed6ab38) at kernel/qobject.cpp:3113
#22 0x000000325cabaf57 in KIO::ConnectionPrivate::dequeue (this=0x273eb10) at /usr/src/debug/kdelibs-4.3.1/kio/kio/connection.cpp:82
#23 0x000000325cabb06d in KIO::Connection::qt_metacall (this=0x27317c0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x2759190)
    at /usr/src/debug/kdelibs-4.3.1/x86_64-redhat-linux-gnu/kio/connection.moc:73
#24 0x0000003f9154eb51 in QObject::event (this=0x27317c0, e=0x1f24760) at kernel/qobject.cpp:1111
#25 0x0000003f91b8f69c in QApplicationPrivate::notify_helper (this=0x18b4c70, receiver=0x27317c0, e=0x1f24760) at kernel/qapplication.cpp:4056
#26 0x0000003f91b968fe in QApplication::notify (this=0x7fff8ed6bc10, receiver=0x27317c0, e=0x1f24760) at kernel/qapplication.cpp:4021
#27 0x0000003299411b56 in KApplication::notify (this=0x7fff8ed6bc10, receiver=0x27317c0, event=0x1f24760) at /usr/src/debug/kdelibs-4.3.1/kdeui/kernel/kapplication.cpp:302
#28 0x0000003f9153f59c in QCoreApplication::notifyInternal (this=0x7fff8ed6bc10, receiver=0x27317c0, event=0x1f24760) at kernel/qcoreapplication.cpp:610
#29 0x0000003f915401a2 in QCoreApplication::sendEvent (event=<value optimized out>, receiver=<value optimized out>) at kernel/qcoreapplication.h:213
#30 QCoreApplicationPrivate::sendPostedEvents (event=<value optimized out>, receiver=<value optimized out>) at kernel/qcoreapplication.cpp:1247
#31 0x0000003f91567cc3 in QCoreApplication::sendPostedEvents () at kernel/qcoreapplication.h:218
#32 postEventSourceDispatch () at kernel/qeventdispatcher_glib.cpp:210
#33 0x00000036c1e3790e in g_main_context_dispatch () from /lib64/libglib-2.0.so.0
#34 0x00000036c1e3b0e8 in ?? () from /lib64/libglib-2.0.so.0
#35 0x00000036c1e3b20a in g_main_context_iteration () from /lib64/libglib-2.0.so.0
#36 0x0000003f91567936 in QEventDispatcherGlib::processEvents (this=0x1887130, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:327
#37 0x0000003f91c21f8e in QGuiEventDispatcherGlib::processEvents (this=0x29cfe00, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#38 0x0000003f9153ded2 in QEventLoop::processEvents (this=<value optimized out>, flags={i = 36}) at kernel/qeventloop.cpp:149
#39 0x0000003f9153e2a4 in QEventLoop::exec (this=0x7fff8ed6bb50, flags={i = 0}) at kernel/qeventloop.cpp:201
#40 0x0000003f91540439 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#41 0x0000000000403d17 in main (argc=<value optimized out>, argv=<value optimized out>) at /usr/src/debug/kdepim-4.3.1/kontact/src/main.cpp:218

Reported using DrKonqi