It is probably bug 188623, but to be sure, we need a backtrace of the crash. For more information, see http://techbase.kde.org/User:DarioAndres/How_to_provide_more_information_about_crash_reports

The crash has reoccurred after going away from rebooting. I now get a KDE Screen Locker Crash Report whenever the screensaver wants to start. The backtrace is pasted at the bottom.

> From: christoph@maxiom.de
> To: robert.goslar@sympatico.ca
> Subject: [Bug 297784] Crashed while trying to change screensaver
> Date: Tue, 10 Apr 2012 00:15:58 +0000
> 
> https://bugs.kde.org/show_bug.cgi?id=297784
> 
> Christoph Feck <christoph@maxiom.de> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |NEEDSINFO
>                  CC|                            |christoph@maxiom.de
>          Resolution|---                         |BACKTRACE
>            Severity|normal                      |crash
> 
> --- Comment #1 from Christoph Feck <christoph@maxiom.de> ---
> It is probably bug 188623, but to be sure, we need a backtrace of the crash.
> For more information, see
> http://techbase.kde.org/User:DarioAndres/How_to_provide_more_information_about_crash_reports
> 
> -- 
> You are receiving this mail because:
> You reported the bug.



Application: System Settings (systemsettings), signal: Segmentation fault
[KCrash Handler]
#6  0xb5cd38d4 in XVisualIDFromVisual (visual=0xdb) at Misc.c:60
#7  0xb6ae5bd4 in qt_x11_getX11InfoForWindow (xinfo=0x84cc9d4, att=...) at kernel/qwidget_x11.cpp:3100
#8  0xb6ae5c7f in qt_x11_getX11InfoForWindow (xinfo=0x84cc9d4, a=...) at kernel/qwidget_x11.cpp:427
#9  0xb6ae9796 in QWidgetPrivate::create_sys (this=0x84cc8b0, window=35659967, initializeWindow=false, destroyOldWindow=true) at kernel/qwidget_x11.cpp:590
#10 0xb6a961af in QWidget::create (this=0x84cc490, window=35659967, initializeWindow=false, destroyOldWindow=true) at kernel/qwidget.cpp:1487
#11 0xb300bd72 in KSWidget::KSWidget (this=0x84cc490, parent=0x839fd20, wf=...) at /usr/src/debug/kde-workspace-4.7.2/kcontrol/screensaver/kswidget.cpp:91
#12 0xb3004c66 in KSSMonitor (parent=<optimized out>, this=0x84cc490) at /usr/src/debug/kde-workspace-4.7.2/kcontrol/screensaver/kssmonitor.h:34
#13 slotPreviewExited (this=0x8391bb0) at /usr/src/debug/kde-workspace-4.7.2/kcontrol/screensaver/scrnsave.cpp:513
#14 KScreenSaver::slotPreviewExited (this=0x8391bb0) at /usr/src/debug/kde-workspace-4.7.2/kcontrol/screensaver/scrnsave.cpp:499
#15 0xb30069eb in KScreenSaver::findSavers (this=0x8391bb0) at /usr/src/debug/kde-workspace-4.7.2/kcontrol/screensaver/scrnsave.cpp:472
#16 0xb3007044 in KScreenSaver::qt_metacall (this=0x8391bb0, _c=QMetaObject::InvokeMetaMethod, _id=<optimized out>, _a=0xbfc182d4) at /usr/src/debug/kde-workspace-4.7.2/build/kcontrol/screensaver/scrnsave.moc:104
#17 0xb647a7ed in metacall (argv=0xbfc182d4, idx=47, cl=QMetaObject::InvokeMetaMethod, object=0x8391bb0) at kernel/qmetaobject.cpp:237
#18 QMetaObject::metacall (object=0x8391bb0, cl=QMetaObject::InvokeMetaMethod, idx=47, argv=0xbfc182d4) at kernel/qmetaobject.cpp:232
#19 0xb6489720 in QMetaObject::activate (sender=0x83de6e8, m=0xb65ab618, local_signal_index=0, argv=0x0) at kernel/qobject.cpp:3287
#20 0xb64d8d75 in QTimer::timeout (this=0x83de6e8) at .moc/release-shared/moc_qtimer.cpp:134
#21 0xb6490f96 in QTimer::timerEvent (this=0x83de6e8, e=0xbfc187ec) at kernel/qtimer.cpp:271
#22 0xb648c684 in QObject::event (this=0x83de6e8, e=0xbfc187ec) at kernel/qobject.cpp:1190
#23 0xb6a42f24 in notify_helper (e=0xbfc187ec, receiver=0x83de6e8, this=0x808d458) at kernel/qapplication.cpp:4481
#24 QApplicationPrivate::notify_helper (this=0x808d458, receiver=0x83de6e8, e=0xbfc187ec) at kernel/qapplication.cpp:4453
#25 0xb6a482b2 in QApplication::notify (this=0xbfc187ec, receiver=0x83de6e8, e=0xbfc187ec) at kernel/qapplication.cpp:4228
#26 0xb75a3681 in KApplication::notify (this=0xbfc18b2c, receiver=0x83de6e8, event=0xbfc187ec) at /usr/src/debug/kdelibs-4.7.2/kdeui/kernel/kapplication.cpp:311
#27 0xb647443e in QCoreApplication::notifyInternal (this=0xbfc18b2c, receiver=0x83de6e8, event=0xbfc187ec) at kernel/qcoreapplication.cpp:787
#28 0xb64a497f in sendEvent (event=<optimized out>, receiver=<optimized out>) at kernel/qcoreapplication.h:215
#29 QTimerInfoList::activateTimers (this=0x8085114) at kernel/qeventdispatcher_unix.cpp:618
#30 0xb64a1ea2 in timerSourceDispatch (source=0x80850e0) at kernel/qeventdispatcher_glib.cpp:184
#31 0xb5885e2f in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#32 0xb5886560 in ?? () from /usr/lib/libglib-2.0.so.0
#33 0xb58867fa in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#34 0xb64a2847 in QEventDispatcherGlib::processEvents (this=0x8060f68, flags=...) at kernel/qeventdispatcher_glib.cpp:422
#35 0xb6af6b1a in QGuiEventDispatcherGlib::processEvents (this=0x8060f68, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#36 0xb647345d in QEventLoop::processEvents (this=0xbfc18a84, flags=...) at kernel/qeventloop.cpp:149
#37 0xb64736a1 in QEventLoop::exec (this=0xbfc18a84, flags=...) at kernel/qeventloop.cpp:201
#38 0xb6477dfa in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1064
#39 0xb6a40da4 in QApplication::exec () at kernel/qapplication.cpp:3755
#40 0x08050d18 in main (argc=) at /usr/src/debug/kde-workspace-4.7.2/systemsettings/app/main.cpp:49

Thanks for the update.

*** This bug has been marked as a duplicate of bug 188623 ***