Application: kontact (4.4.2)
KDE Platform Version: 4.4.2 (KDE 4.4.2)
Qt Version: 4.6.2
Operating System: Linux 2.6.32-22-generic i686
Distribution: Ubuntu 10.04 LTS

-- Information about the crash:
This happens to me frequently, but not always. 

Steps to reproduce:

1. Start Kontact, switch to mail, which includes an IMAP account
2. Lose connection to IMAP account (happens to me usually due to poor wifi)
3. Quit Kontact
4. Restart Kontact
=> crash

Everything works fine upon second restart.

The crash can be reproduced some of the time.

 -- Backtrace:
Application: Kontact (kontact), signal: Segmentation fault
[Current thread is 1 (Thread 0xb7808990 (LWP 1758))]

Thread 2 (Thread 0xb3202b70 (LWP 1762)):
#0  0x04fc7e16 in clock_gettime () from /lib/tls/i686/cmov/librt.so.1
#1  0x00e1a6fb in qt_gettime () at kernel/qcore_unix.cpp:111
#2  0x00e1f825 in QTimerInfoList::updateCurrentTime (this=0x8c9ed7c) at kernel/qeventdispatcher_unix.cpp:340
#3  0x00e1f86a in QTimerInfoList::timerWait (this=0x8c9ed7c, tm=...) at kernel/qeventdispatcher_unix.cpp:443
#4  0x00e1d818 in timerSourcePrepareHelper (src=<value optimized out>, timeout=0xb32020ac) at kernel/qeventdispatcher_glib.cpp:136
#5  0x00e1d8a5 in timerSourcePrepare (source=0x0, timeout=0x4fcbff4) at kernel/qeventdispatcher_glib.cpp:169
#6  0x0543faca in g_main_context_prepare () from /lib/libglib-2.0.so.0
#7  0x0543fee9 in ?? () from /lib/libglib-2.0.so.0
#8  0x054404b8 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#9  0x00e1d60f in QEventDispatcherGlib::processEvents (this=0x824aa68, flags=...) at kernel/qeventdispatcher_glib.cpp:414
#10 0x00df0059 in QEventLoop::processEvents (this=0xb3202270, flags=) at kernel/qeventloop.cpp:149
#11 0x00df04aa in QEventLoop::exec (this=0xb3202270, flags=...) at kernel/qeventloop.cpp:201
#12 0x00cec5a8 in QThread::exec (this=0x824a418) at thread/qthread.cpp:487
#13 0x00dcfc1b in QInotifyFileSystemWatcherEngine::run (this=0x824a418) at io/qfilesystemwatcher_inotify.cpp:248
#14 0x00cef32e in QThreadPrivate::start (arg=0x824a418) at thread/qthread_unix.cpp:248
#15 0x03ca496e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#16 0x03f58a0e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb7808990 (LWP 1758)):
[KCrash Handler]
#6  QBasicAtomicInt::ref (this=0x86ee5e0) at /usr/include/qt4/QtCore/qatomic_i386.h:120
#7  QString (this=0x86ee5e0) at /usr/include/qt4/QtCore/qstring.h:715
#8  KontactInterface::Plugin::identifier (this=0x86ee5e0) at ../../kontactinterface/plugin.cpp:101
#9  0x00891eae in Kontact::MainWindow::activateInitialPluginModule (this=0x81ee198) at ../../../kontact/src/mainwindow.cpp:289
#10 0x00891f64 in Kontact::MainWindow::setInitialActivePluginModule (this=0x81ee198, module=...) at ../../../kontact/src/mainwindow.cpp:266
#11 0x0804bd1f in KontactApp::newInstance (this=0xbfd088e4) at ../../../kontact/src/main.cpp:149
#12 0x00a93950 in KUniqueApplicationAdaptor::newInstance (this=0x829efc0, asn_id=..., args=...) at ../../kdeui/kernel/kuniqueapplication.cpp:454
#13 0x00a940b2 in KUniqueApplicationAdaptor::qt_metacall (this=0x829efc0, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0xbfd07e3c) at ./kuniqueapplication_p.moc:81
#14 0x01dffb34 in QDBusConnectionPrivate::deliverCall (this=0x81d9d60, object=0x829efc0, msg=..., metaTypes=..., slotIdx=4) at qdbusintegrator.cpp:904
#15 0x01e00e45 in QDBusConnectionPrivate::activateCall (this=0x81d9d60, object=0x829efc0, flags=337, msg=...) at qdbusintegrator.cpp:816
#16 0x01e01880 in QDBusConnectionPrivate::activateObject (this=0x81d9d60, node=..., msg=..., pathStartPos=16) at qdbusintegrator.cpp:1364
#17 0x01e01b1a in QDBusActivateObjectEvent::placeMetaCall (this=0x96f8368) at qdbusintegrator.cpp:1477
#18 0x00e023fe in QObject::event (this=0xbfd088e4, e=0x96f8368) at kernel/qobject.cpp:1248
#19 0x00df150b in QCoreApplication::event (this=0xbfd088e4, e=0x96f8368) at kernel/qcoreapplication.cpp:1533
#20 0x01040e46 in QApplication::event (this=0xbfd088e4, e=0x96f8368) at kernel/qapplication.cpp:2353
#21 0x0103c4dc in QApplicationPrivate::notify_helper (this=0x81edeb8, receiver=0xbfd088e4, e=0x96f8368) at kernel/qapplication.cpp:4300
#22 0x0104305e in QApplication::notify (this=0xbfd088e4, receiver=0xbfd088e4, e=0x96f8368) at kernel/qapplication.cpp:3704
#23 0x00a8bf2a in KApplication::notify (this=0xbfd088e4, receiver=0xbfd088e4, event=0x96f8368) at ../../kdeui/kernel/kapplication.cpp:302
#24 0x00df1a3b in QCoreApplication::notifyInternal (this=0xbfd088e4, receiver=0xbfd088e4, event=0x96f8368) at kernel/qcoreapplication.cpp:704
#25 0x00df4473 in QCoreApplication::sendEvent (receiver=0x0, event_type=0, data=0x81c24e0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#26 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x81c24e0) at kernel/qcoreapplication.cpp:1345
#27 0x00df45dd in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1238
#28 0x00e1dadf in QCoreApplication::sendPostedEvents (s=0x81f16b0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:220
#29 postEventSourceDispatch (s=0x81f16b0) at kernel/qeventdispatcher_glib.cpp:276
#30 0x0543c5e5 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#31 0x054402d8 in ?? () from /lib/libglib-2.0.so.0
#32 0x054404b8 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#33 0x00e1d5d5 in QEventDispatcherGlib::processEvents (this=0x81c2070, flags=...) at kernel/qeventdispatcher_glib.cpp:412
#34 0x010fc135 in QGuiEventDispatcherGlib::processEvents (this=0x81c2070, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#35 0x00df0059 in QEventLoop::processEvents (this=0xbfd08844, flags=) at kernel/qeventloop.cpp:149
#36 0x00df04aa in QEventLoop::exec (this=0xbfd08844, flags=...) at kernel/qeventloop.cpp:201
#37 0x00df469f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:981
#38 0x0103c577 in QApplication::exec () at kernel/qapplication.cpp:3579
#39 0x0804b472 in main (argc=1, argv=0xbfd08b04) at ../../../kontact/src/main.cpp:224

Reported using DrKonqi