Here using:

Qt: 4.5.0-rc1
KDE: 4.2.63 (KDE 4.2.63 (KDE 4.3 >= 20090212))
kdelibs svn rev. 927117 / kdebase svn rev. 927117
kdepim svn rev. 928042
on ArchLinux i686 - Kernel 2.6.28.4

Kontact crashes when the KMail component is disabled and after going to Settings, enabling the Mail component and selecting one of its siblings

Not sure if its a KMail bug or a KDELibs one (for allowing me to click on the KMail siblings if they aren't ready to be shown)

Steps to reproduce:

- Open Kontact
- Go to Configure Kontact
- Disable the KMail component
- Close Kontact

- Re-open Kontact
(the KMail component is disabled and it doesn't appears on the sidebar)
- Go to Configure Kontact
- Enable the KMail component
- Without accepting, click on one of the KMail siblings in the configuration dialog to show its configuration page

Kontact crashes with the following backtrace:

Application: Kontact (kontact), signal SIGSEGV
[Current thread is 0 (LWP 10324)]

Thread 3 (Thread 0xb17aeb90 (LWP 10326)):
#0  0xb801f424 in __kernel_vsyscall ()
#1  0xb6743f82 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#2  0xb67a25dc in QWaitCondition::wait (this=0x9667de0, mutex=0x9667ddc, time=30000) at thread/qwaitcondition_unix.cpp:80
#3  0xb6797c66 in QThreadPoolThread::run (this=0x9663da0) at concurrent/qthreadpool.cpp:135
#4  0xb67a1a20 in QThreadPrivate::start (arg=0x9663da0) at thread/qthread_unix.cpp:184
#5  0xb6740155 in start_thread () from /lib/libpthread.so.0
#6  0xb5be6a5e in clone () from /lib/libc.so.6

Thread 2 (Thread 0xb0c92b90 (LWP 10330)):
#0  0xb801f424 in __kernel_vsyscall ()
#1  0xb5bdfab1 in select () from /lib/libc.so.6
#2  0xb6871937 in QProcessManager::run (this=0x9256058) at io/qprocess_unix.cpp:300
#3  0xb67a1a20 in QThreadPrivate::start (arg=0x9256058) at thread/qthread_unix.cpp:184
#4  0xb6740155 in start_thread () from /lib/libpthread.so.0
#5  0xb5be6a5e in clone () from /lib/libc.so.6

Thread 1 (Thread 0xb4bbb700 (LWP 10324)):
[KCrash Handler]
#6  KMMainWidget::actionCollections (this=0x0) at /home/kde-devel/kde/src/KDE/kdepim/kmail/kmmainwidget.h:366
#7  0xaf88e7d4 in CustomTemplates (this=0x9c16ba8, parent=0x9c15028, name=0x0) at /home/kde-devel/kde/src/KDE/kdepim/kmail/customtemplates.cpp:88
#8  0xaf486bed in ComposerPageCustomTemplatesTab (this=0x9c15028, parent=0x0) at /home/kde-devel/kde/src/KDE/kdepim/kmail/configuredialog.cpp:3062
#9  0xaf4b1773 in ComposerPage (this=0x9bdcaa0, instance=@0xbfc38788, parent=0x9bb18a8) at /home/kde-devel/kde/src/KDE/kdepim/kmail/configuredialog.cpp:2740
#10 0xafc3533e in create_kmail_config_composer (parent=0x9bb18a8) at /home/kde-devel/kde/src/KDE/kdepim/kmail/kcm_kmail.cpp:60
#11 0xb58365bc in KCModuleLoader::loadModule (mod=@0x9bd4568, report=KCModuleLoader::Inline, parent=0x9bb18a8, args=@0x9bd4550) at /home/kde-devel/kde/src/KDE/kdelibs/kutils/kcmoduleloader.cpp:111
#12 0xb583bafd in KCModuleProxyPrivate::loadModule (this=0x9bd4550) at /home/kde-devel/kde/src/KDE/kdelibs/kutils/kcmoduleproxy.cpp:105
#13 0xb583cc33 in KCModuleProxy::realModule (this=0x9bb18a8) at /home/kde-devel/kde/src/KDE/kdelibs/kutils/kcmoduleproxy.cpp:81
#14 0xb583cfd8 in KCModuleProxy::showEvent (this=0x9bb18a8, ev=0xbfc38f9c) at /home/kde-devel/kde/src/KDE/kdelibs/kutils/kcmoduleproxy.cpp:192
#15 0xb5f04eed in QWidget::event (this=0x9bb18a8, event=0xbfc38f9c) at kernel/qwidget.cpp:7710
#16 0xb5eab42c in QApplicationPrivate::notify_helper (this=0x9253118, receiver=0x9bb18a8, e=0xbfc38f9c) at kernel/qapplication.cpp:4051
#17 0xb5eb4072 in QApplication::notify (this=0xbfc3a5bc, receiver=0x9bb18a8, e=0xbfc38f9c) at kernel/qapplication.cpp:4016
#18 0xb6ddf11d in KApplication::notify (this=0xbfc3a5bc, receiver=0x9bb18a8, event=0xbfc38f9c) at /home/kde-devel/kde/src/KDE/kdelibs/kdeui/kernel/kapplication.cpp:307
#19 0xb6890f4b in QCoreApplication::notifyInternal (this=0xbfc3a5bc, receiver=0x9bb18a8, event=0xbfc38f9c) at kernel/qcoreapplication.cpp:590
#20 0xb5f061ab in QWidgetPrivate::show_helper (this=0x9bcbe98) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:208
#21 0xb5f067ae in QWidget::setVisible (this=0x9bb18a8, visible=true) at kernel/qwidget.cpp:6936
#22 0xb5ee9e61 in QStackedLayout::setCurrentIndex (this=0x9aee3b0, index=4) at ../../include/QtGui/../../src/gui/kernel/qwidget.h:468
#23 0xb5ee9fed in QStackedLayout::setCurrentWidget (this=0x9aee3b0, widget=0x9bb18a8) at kernel/qstackedlayout.cpp:362
#24 0xb632e88c in QStackedWidget::setCurrentWidget (this=0x9aee388, widget=0x9bb18a8) at widgets/qstackedwidget.cpp:243
#25 0xb6e11637 in KPageViewPrivate::_k_pageSelected (this=0x9710790, index=@0x9b39e20, previous=@0x9bd3698) at /home/kde-devel/kde/src/KDE/kdelibs/kdeui/paged/kpageview.cpp:226
#26 0xb6e120d7 in KPageView::qt_metacall (this=0x9506a10, _c=QMetaObject::InvokeMetaMethod, _id=3, _a=0xbfc391e8) at /home/kde-devel/kde/build/KDE/kdelibs/kdeui/kpageview.moc:94
#27 0xb6e15c7a in KPageWidget::qt_metacall (this=0x9506a10, _c=QMetaObject::InvokeMetaMethod, _id=30, _a=0xbfc391e8) at /home/kde-devel/kde/build/KDE/kdelibs/kdeui/kpagewidget.moc:70
#28 0xb68a72b1 in QMetaObject::activate (sender=0x9bd7078, from_signal_index=<value optimized out>, to_signal_index=5, argv=0xbfc391e8) at kernel/qobject.cpp:3052
#29 0xb68a78b2 in QMetaObject::activate (sender=0x9bd7078, m=0xb6615a4c, local_signal_index=1, argv=0xbfc391e8) at kernel/qobject.cpp:3127
#30 0xb644edf9 in QItemSelectionModel::currentChanged (this=0x9bd7078, _t1=@0x9b39e20, _t2=@0x9bd3698) at .moc/debug-shared/moc_qitemselectionmodel.cpp:153
#31 0xb644ef9d in QItemSelectionModel::setCurrentIndex (this=0x9bd7078, index=@0x9b39e20, command={i = -1077701840}) at itemviews/qitemselectionmodel.cpp:1118
#32 0xb63fcf46 in QAbstractItemView::mousePressEvent (this=0x9af36d8, event=0xbfc39c7c) at itemviews/qabstractitemview.cpp:1503
#33 0xb6447940 in QTreeView::mousePressEvent (this=0x9af36d8, event=0xbfc39c7c) at itemviews/qtreeview.cpp:1772
#34 0xb5f05196 in QWidget::event (this=0x9af36d8, event=0xbfc39c7c) at kernel/qwidget.cpp:7507
#35 0xb62c4753 in QFrame::event (this=0x9af36d8, e=0xbfc39c7c) at widgets/qframe.cpp:554
#36 0xb635cf0f in QAbstractScrollArea::viewportEvent (this=0x9af36d8, e=0x127) at widgets/qabstractscrollarea.cpp:957
#37 0xb6403d1f in QAbstractItemView::viewportEvent (this=0x9af36d8, event=0xbfc39c7c) at itemviews/qabstractitemview.cpp:1461
#38 0xb643f6f2 in QTreeView::viewportEvent (this=0x9af36d8, event=0xbfc39c7c) at itemviews/qtreeview.cpp:1252
#39 0xb635f455 in QAbstractScrollAreaFilter::eventFilter (this=0x9bce3a8, o=0x9ab6b48, e=0xbfc39c7c) at widgets/qabstractscrollarea_p.h:95
#40 0xb689095a in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=0x9253118, receiver=0x9ab6b48, event=0xbfc39c7c) at kernel/qcoreapplication.cpp:710
#41 0xb5eab40a in QApplicationPrivate::notify_helper (this=0x9253118, receiver=0x9ab6b48, e=0xbfc39c7c) at kernel/qapplication.cpp:4047
#42 0xb5eb48fc in QApplication::notify (this=0xbfc3a5bc, receiver=0x9ab6b48, e=0xbfc39c7c) at kernel/qapplication.cpp:3753
#43 0xb6ddf11d in KApplication::notify (this=0xbfc3a5bc, receiver=0x9ab6b48, event=0xbfc39c7c) at /home/kde-devel/kde/src/KDE/kdelibs/kdeui/kernel/kapplication.cpp:307
#44 0xb6890f4b in QCoreApplication::notifyInternal (this=0xbfc3a5bc, receiver=0x9ab6b48, event=0xbfc39c7c) at kernel/qcoreapplication.cpp:590
#45 0xb5eb39af in QApplicationPrivate::sendMouseEvent (receiver=0x9ab6b48, event=0xbfc39c7c, alienWidget=0x9ab6b48, nativeWidget=0x9b89450, buttonDown=0xb6621f40, lastMouseReceiver=@0xb6621f44)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:211
#46 0xb5f1d135 in QETWidget::translateMouseEvent (this=0x9b89450, event=0xbfc3a1dc) at kernel/qapplication_x11.cpp:4414
#47 0xb5f1c19d in QApplication::x11ProcessEvent (this=0xbfc3a5bc, event=0xbfc3a1dc) at kernel/qapplication_x11.cpp:3532
#48 0xb5f43c8a in x11EventSourceDispatch (s=0x92558d8, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:141
#49 0xb5111311 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#50 0xb51149a3 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#51 0xb5114b61 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#52 0xb68bb838 in QEventDispatcherGlib::processEvents (this=0x925b4a8, flags={i = -1077697640}) at kernel/qeventdispatcher_glib.cpp:318
#53 0xb5f433e5 in QGuiEventDispatcherGlib::processEvents (this=0x925b4a8, flags={i = -1077697592}) at kernel/qguieventdispatcher_glib.cpp:197
#54 0xb688f98a in QEventLoop::processEvents (this=0xbfc3a430, flags={i = -1077697528}) at kernel/qeventloop.cpp:144
#55 0xb688fb4a in QEventLoop::exec (this=0xbfc3a430, flags={i = -1077697480}) at kernel/qeventloop.cpp:191
#56 0xb6894bc1 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:872
#57 0xb5eab157 in QApplication::exec () at kernel/qapplication.cpp:3526
#58 0x0804be97 in main (argc=1, argv=0xbfc3a7b4) at /home/kde-devel/kde/src/KDE/kdepim/kontact/src/main.cpp:218