Version:            (using KDE 4.2.3)
OS:                AIX
Installed from:    Ubuntu Packages

I do not know if this report is of any use for you since you are already working on KDE 4.3. I have had a repeating crash which occured the first time while I was trying to configure the networkmanager applet to use mobile broadband. After this plasma crashed again and again and again .... until I kill the networkmanager via a terminal. Then I removed the networkmanager applet, restarted the networkmanager, added the applet again and everything worked. 
Here is the crash report:
Anwendung: Plasma-Arbeitsfläche (plasma), Signal SIGSEGV
[Current thread is 0 (LWP 3837)]

Thread 3 (Thread 0xa8cfcb90 (LWP 4000)):
#0  0xb803d430 in __kernel_vsyscall ()
#1  0xb51fa0e5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb63ac2ed in pthread_cond_wait () from /lib/tls/i686/cmov/libc.so.6
#3  0xb65905b2 in QWaitCondition::wait (this=0x9a6fb88, mutex=0x9a6fb84, time=4294967295) at thread/qwaitcondition_unix.cpp:87
#4  0xb79eeae2 in QHostInfoAgent::run (this=0x9a6fb78) at kernel/qhostinfo.cpp:260
#5  0xb658f56e in QThreadPrivate::start (arg=0x9a6fb78) at thread/qthread_unix.cpp:189
#6  0xb51f64ff in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#7  0xb639d49e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 2 (Thread 0xa8319b90 (LWP 4011)):
#0  0xb803d430 in __kernel_vsyscall ()
#1  0xb51fa0e5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb63ac2ed in pthread_cond_wait () from /lib/tls/i686/cmov/libc.so.6
#3  0xb65905b2 in QWaitCondition::wait (this=0x98536f0, mutex=0x98536ec, time=4294967295) at thread/qwaitcondition_unix.cpp:87
#4  0xa958ab9a in RenderThread::run (this=0x98536e4) at /build/buildd/kdebase-workspace-4.2.3/plasma/wallpapers/image/renderthread.cpp:91
#5  0xb658f56e in QThreadPrivate::start (arg=0x98536e4) at thread/qthread_unix.cpp:189
#6  0xb51f64ff in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#7  0xb639d49e in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb4ce7710 (LWP 3837)):
[KCrash Handler]
#6  WirelessConnectionInspector::watchedNetworks (this=0x700075) at /usr/include/qt4/QtCore/qlist.h:111
#7  0xa90127dd in InterfaceGroup::updateConnections (this=0x9b53008) at /build/buildd/plasma-widget-network-manager-0.0+svn966653/applet/interfacegroup.cpp:147
#8  0xa8ffdbfb in InterfaceGroup::qt_metacall (this=0x9b53008, _c=QMetaObject::InvokeMetaMethod, _id=8, _a=0xbfff4888)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/obj-i486-linux-gnu/applet/moc_interfacegroup.cpp:91
#9  0xb6699a58 in QMetaObject::activate (sender=0x9b53008, from_signal_index=5, to_signal_index=5, argv=0x0) at kernel/qobject.cpp:3120
#10 0xb669a6e2 in QMetaObject::activate (sender=0x9b53008, m=0xa902ffe0, local_signal_index=0, argv=0x0) at kernel/qobject.cpp:3194
#11 0xa8ffc9d7 in ConnectionList::connectionListUpdated (this=0x9b53008) at /build/buildd/plasma-widget-network-manager-0.0+svn966653/obj-i486-linux-gnu/applet/moc_connectionlist.cpp:97
#12 0xa9001a2d in ConnectionList::serviceDisappeared (this=0x9b53008, settings=0x991c1f0) at /build/buildd/plasma-widget-network-manager-0.0+svn966653/applet/connectionlist.cpp:99
#13 0xa8ffdac4 in ConnectionList::qt_metacall (this=0x9b53008, _c=QMetaObject::InvokeMetaMethod, _id=6, _a=0xbfff4a4c)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/obj-i486-linux-gnu/applet/moc_connectionlist.cpp:86
#14 0xa8ffdbba in InterfaceGroup::qt_metacall (this=0x9b53008, _c=QMetaObject::InvokeMetaMethod, _id=11, _a=0xbfff4a4c)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/obj-i486-linux-gnu/applet/moc_interfacegroup.cpp:78
#15 0xb6699a58 in QMetaObject::activate (sender=0x991c1f0, from_signal_index=10, to_signal_index=10, argv=0xbfff4a4c) at kernel/qobject.cpp:3120
#16 0xb669a6e2 in QMetaObject::activate (sender=0x991c1f0, m=0xa94ebe44, local_signal_index=3, argv=0xbfff4a4c) at kernel/qobject.cpp:3194
#17 0xa94e4a63 in NetworkManagerSettings::disappeared (this=0x991c1f0, _t1=0x991c1f0)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/obj-i486-linux-gnu/libs/dbus/networkmanagersettings.moc:126
#18 0xa94e5ab4 in NetworkManagerSettings::serviceOwnerChanged (this=0x991c1f0, changedService=@0x9bd2ba8, oldOwner=@0x9b4ee88, newOwner=@0x9b4ef28)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/libs/dbus/networkmanagersettings.cpp:119
#19 0xa94e6863 in NetworkManagerSettings::qt_metacall (this=0x991c1f0, _c=QMetaObject::InvokeMetaMethod, _id=8, _a=0xbfff4b74)
    at /build/buildd/plasma-widget-network-manager-0.0+svn966653/obj-i486-linux-gnu/libs/dbus/networkmanagersettings.moc:93
#20 0xb6699a58 in QMetaObject::activate (sender=0x994fa50, from_signal_index=7, to_signal_index=7, argv=0xbfff4b74) at kernel/qobject.cpp:3120
#21 0xb669a6e2 in QMetaObject::activate (sender=0x994fa50, m=0xb67ebca8, local_signal_index=2, argv=0xbfff4b74) at kernel/qobject.cpp:3194
#22 0xb67d4a2f in QDBusConnectionInterface::serviceOwnerChanged (this=0x994fa50, _t1=@0x9bd2ba8, _t2=@0x9b4ee88, _t3=@0x9b4ef28) at .moc/release-shared/moc_qdbusconnectioninterface.cpp:204
#23 0xb67d4fbb in QDBusConnectionInterface::qt_metacall (this=0x994fa50, _c=QMetaObject::InvokeMetaMethod, _id=2, _a=0xbfff4d14) at .moc/release-shared/moc_qdbusconnectioninterface.cpp:131
#24 0xb6699a58 in QMetaObject::activate (sender=0x994fa50, from_signal_index=11, to_signal_index=11, argv=0xbfff4d14) at kernel/qobject.cpp:3120
#25 0xb669a6e2 in QMetaObject::activate (sender=0x994fa50, m=0xb67ebca8, local_signal_index=6, argv=0xbfff4d14) at kernel/qobject.cpp:3194
#26 0xb67d48df in QDBusConnectionInterface::NameOwnerChanged (this=0x994fa50, _t1=@0x9bd2ba8, _t2=@0x9b4ee88, _t3=@0x9b4ef28) at .moc/release-shared/moc_qdbusconnectioninterface.cpp:232
#27 0xb67d4f2b in QDBusConnectionInterface::qt_metacall (this=0x994fa50, _c=QMetaObject::InvokeMetaMethod, _id=6, _a=0xbfff4f58) at .moc/release-shared/moc_qdbusconnectioninterface.cpp:135
#28 0xb679ae2a in QDBusConnectionPrivate::deliverCall (this=0x992df00, object=0x994fa50, msg=@0x9cf0ccc, metaTypes=@0x9cf0cd0, slotIdx=11) at qdbusintegrator.cpp:891
#29 0xb67a2e57 in QDBusCallDeliveryEvent::placeMetaCall (this=0x9cf0ca0, object=0x994fa50) at qdbusintegrator_p.h:101
#30 0xb6694150 in QObject::event (this=0x994fa50, e=0x9cf0ca0) at kernel/qobject.cpp:1118
#31 0xb690ebcc in QApplicationPrivate::notify_helper (this=0x9709dc0, receiver=0x994fa50, e=0x9cf0ca0) at kernel/qapplication.cpp:4057
#32 0xb6916ede in QApplication::notify (this=0x97085d0, receiver=0x994fa50, e=0x9cf0ca0) at kernel/qapplication.cpp:3604
#33 0xb7767e5d in KApplication::notify (this=0x97085d0, receiver=0x994fa50, event=0x9cf0ca0) at /build/buildd/kde4libs-4.2.3/kdeui/kernel/kapplication.cpp:307
#34 0xb66837ab in QCoreApplication::notifyInternal (this=0x97085d0, receiver=0x994fa50, event=0x9cf0ca0) at kernel/qcoreapplication.cpp:610
#35 0xb6684405 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x96c92c8) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#36 0xb66845fd in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1140
#37 0xb66af58f in postEventSourceDispatch (s=0x970bf10) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:218
#38 0xb4ff4b88 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#39 0xb4ff80eb in ?? () from /usr/lib/libglib-2.0.so.0
#40 0xb4ff8268 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#41 0xb66af1d8 in QEventDispatcherGlib::processEvents (this=0x96cc270, flags={i = -1073785512}) at kernel/qeventdispatcher_glib.cpp:324
#42 0xb69b0765 in QGuiEventDispatcherGlib::processEvents (this=0x96cc270, flags={i = -1073785464}) at kernel/qguieventdispatcher_glib.cpp:202
#43 0xb6681dda in QEventLoop::processEvents (this=0xbfff5600, flags={i = -1073785400}) at kernel/qeventloop.cpp:149
#44 0xb668221a in QEventLoop::exec (this=0xbfff5600, flags={i = -1073785336}) at kernel/qeventloop.cpp:200
#45 0xb66846c9 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#46 0xb690ea47 in QApplication::exec () at kernel/qapplication.cpp:3526
#47 0xb7fdab56 in kdemain (argc=1, argv=0xbfff57b4) at /build/buildd/kdebase-workspace-4.2.3/plasma/shells/desktop/main.cpp:54
#48 0x08048712 in main (argc=-1459419480, argv=0x9b5d840) at /build/buildd/kdebase-workspace-4.2.3/obj-i486-linux-gnu/plasma/shells/desktop/plasma_qgv_dummy.cpp:3