This is probably related to bug 189959
If you can reproduce the crash at will, may you read
http://techbase.kde.org/Development/Tutorials/Debugging/How_to_create_useful_crash_reports
and post a complete backtrace here? You may need to install some debug info
packages. Thanks

I am bit busy managing my KDE4 transition. So it will take a while, if I forget, just send me a reminder. But what is missing in the above backtrace? I thought I had all debug packages installed?

No problem
The debug symbols missing are those from the "libknmstorage.so.4" file.
Thanks

I do not know if this better, because it is bit complicated to know in Kubuntu which debug-packages need to be installed for that. I could not find any related debug-info, so installed anything I could find.

Application: KDE-Dienst (kded4), signal: Segmentation fault
[KCrash Handler]
#6  Knm::Connection::settings (this=0x871ce08) at /usr/include/qt4/QtCore/qatomic_i386.h:120
#7  0xb4583c1e in Knm::ConnectionPersistence::walletOpenedForRead (this=0x88bbb88, success=true)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/libs/storage/connectionpersistence.cpp:243
#8  0xb457d7a7 in Knm::ConnectionPersistence::qt_metacall (this=0x88bbb88, _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0xbfce191c)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/obj-i486-linux-gnu/libs/storage/moc_connectionpersistence.cpp:72
#9  0xb6a68a58 in QMetaObject::activate (sender=0x89116d8, from_signal_index=8, to_signal_index=8, argv=0xbfce191c) at kernel/qobject.cpp:3120
#10 0xb6a696e2 in QMetaObject::activate (sender=0x89116d8, m=0xb7cdc5a4, local_signal_index=4, argv=0xbfce191c) at kernel/qobject.cpp:3194
#11 0xb7bbc379 in KWallet::Wallet::walletOpened (this=0x89116d8, _t1=true) at /build/buildd/kde4libs-4.2.85/obj-i486-linux-gnu/kdeui/kwallet.moc:139
#12 0xb7bbc680 in KWallet::Wallet::walletAsyncOpened (this=0x89116d8, tId=10, handle=1346339274) at /build/buildd/kde4libs-4.2.85/kdeui/util/kwallet.cpp:724
#13 0xb7bbd42d in KWallet::Wallet::qt_metacall (this=0x89116d8, _c=QMetaObject::InvokeMetaMethod, _id=9, _a=0xbfce1a38) at /build/buildd/kde4libs-4.2.85/obj-i486-linux-gnu/kdeui/kwallet.moc:99
#14 0xb6a68a58 in QMetaObject::activate (sender=0x872e2c0, from_signal_index=9, to_signal_index=9, argv=0xbfce1a38) at kernel/qobject.cpp:3120
#15 0xb6a696e2 in QMetaObject::activate (sender=0x872e2c0, m=0xb7ce2540, local_signal_index=4, argv=0xbfce1a38) at kernel/qobject.cpp:3194
#16 0xb7c92809 in OrgKdeKWalletInterface::walletAsyncOpened (this=0x872e2c0, _t1=10, _t2=1346339274) at /build/buildd/kde4libs-4.2.85/obj-i486-linux-gnu/kdeui/kwallet_interface.moc:300
#17 0xb7c94490 in OrgKdeKWalletInterface::qt_metacall (this=0x872e2c0, _c=QMetaObject::InvokeMetaMethod, _id=4, _a=0xbfce1f48)
    at /build/buildd/kde4libs-4.2.85/obj-i486-linux-gnu/kdeui/kwallet_interface.moc:176
#18 0xb6b69e2a in QDBusConnectionPrivate::deliverCall (this=0x8673c30, object=0x872e2c0, msg=@0x86a2234, metaTypes=@0x86a2238, slotIdx=9) at qdbusintegrator.cpp:891
#19 0xb6b71e57 in QDBusCallDeliveryEvent::placeMetaCall (this=0x86a2208, object=0x872e2c0) at qdbusintegrator_p.h:101
#20 0xb6a63150 in QObject::event (this=0x872e2c0, e=0x86a2208) at kernel/qobject.cpp:1118
#21 0xb6f0abcc in QApplicationPrivate::notify_helper (this=0x8667b88, receiver=0x872e2c0, e=0x86a2208) at kernel/qapplication.cpp:4057
#22 0xb6f12ede in QApplication::notify (this=0xbfce26ac, receiver=0x872e2c0, e=0x86a2208) at kernel/qapplication.cpp:3604
#23 0xb7b2dc9d in KApplication::notify (this=0xbfce26ac, receiver=0x872e2c0, event=0x86a2208) at /build/buildd/kde4libs-4.2.85/kdeui/kernel/kapplication.cpp:307
#24 0xb6a527ab in QCoreApplication::notifyInternal (this=0xbfce26ac, receiver=0x872e2c0, event=0x86a2208) at kernel/qcoreapplication.cpp:610
#25 0xb6a53405 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x864e2c8) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#26 0xb6a535fd in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1140
#27 0xb6a7e58f in postEventSourceDispatch (s=0x8669d20) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#28 0xb6262b88 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#29 0xb62660eb in ?? () from /usr/lib/libglib-2.0.so.0
#30 0xb6266268 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#31 0xb6a7e1d8 in QEventDispatcherGlib::processEvents (this=0x8667b68, flags={i = -1077009080}) at kernel/qeventdispatcher_glib.cpp:324
#32 0xb6fac765 in QGuiEventDispatcherGlib::processEvents (this=0x8667b68, flags={i = -1077009032}) at kernel/qguieventdispatcher_glib.cpp:202
#33 0xb6a50dda in QEventLoop::processEvents (this=0xbfce25f0, flags={i = -1077008968}) at kernel/qeventloop.cpp:149
#34 0xb6a5121a in QEventLoop::exec (this=0xbfce25f0, flags={i = -1077008904}) at kernel/qeventloop.cpp:200
#35 0xb6a536c9 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#36 0xb6f0aa47 in QApplication::exec () at kernel/qapplication.cpp:3526
#37 0xb7f7ed30 in kdemain (argc=1, argv=0xbfce28b4) at /build/buildd/kde4libs-4.2.85/kded/kded.cpp:938
#38 0x080486b2 in main (argc=) at /build/buildd/kde4libs-4.2.85/obj-i486-linux-gnu/kded/kded4_dummy.cpp:3

Now it is a lot better. Bug 194464 looks related.

*** This bug has been marked as a duplicate of bug 194464 ***