Version:            (using KDE 4.3.2)
OS:                Linux
Installed from:    Debian testing/unstable Packages

This reproduces it for me:

Create a new event, with time associated; enable recurrence - weekly. I saved it in a file resource.
Drag and drop one event to another day and get the "Changing Recurring Item" dialogue. The outcome is different for each choice:
 - Only This Item: click the file resource for saving; crash. When re-opening korganizer, the event is gone from the original day, but not saved to the new day.
 - Also Future Items: click file resource; crash. When re-opening, all future events are gone.
 - All Occurences: nothing happens -- the events don't get moved.

Here's the backtrace for "Only This Item":

Application: KOrganizer (korganizer), signal: Segmentation fault
The current source language is "auto; currently c".
[KCrash Handler]
#5  0x0000003c0db025b2 in KOrg::IncidenceMonthItem::updateDates (this=<value optimized out>, startOffset=<value optimized out>, endOffset=<value optimized out>)
    at ../../korganizer/views/monthview/monthitem.cpp:480
#6  0x0000003c0db029d1 in KOrg::IncidenceMonthItem::finalizeMove (this=<value optimized out>, newStartDate=<value optimized out>) at ../../korganizer/views/monthview/monthitem.cpp:385
#7  0x0000003c0db07cb9 in KOrg::MonthScene::mouseReleaseEvent (this=<value optimized out>, mouseEvent=<value optimized out>) at ../../korganizer/views/monthview/monthscene.cpp:616
#8  0x0000003c073a03d0 in QGraphicsScene::event (this=<value optimized out>, event=<value optimized out>) at graphicsview/qgraphicsscene.cpp:3808
#9  0x0000003c06dd801d in QApplicationPrivate::notify_helper (this=<value optimized out>, receiver=<value optimized out>, e=<value optimized out>) at kernel/qapplication.cpp:4065
#10 0x0000003c06de007a in QApplication::notify (this=<value optimized out>, receiver=<value optimized out>, e=<value optimized out>) at kernel/qapplication.cpp:4030
#11 0x0000003c080240db in KApplication::notify (this=<value optimized out>, receiver=<value optimized out>, event=<value optimized out>) at ../../kdeui/kernel/kapplication.cpp:302
#12 0x000000308eb51c9c in QCoreApplication::notifyInternal (this=<value optimized out>, receiver=<value optimized out>, event=<value optimized out>) at kernel/qcoreapplication.cpp:610
#13 0x0000003c073b0b5b in QCoreApplication::sendEvent (this=<value optimized out>, event=<value optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:213
#14 QGraphicsView::mouseReleaseEvent (this=<value optimized out>, event=<value optimized out>) at graphicsview/qgraphicsview.cpp:3382
#15 0x0000003c06e2837f in QWidget::event (this=<value optimized out>, event=<value optimized out>) at kernel/qwidget.cpp:7554
#16 0x0000003c0719092b in QFrame::event (this=<value optimized out>, e=<value optimized out>) at widgets/qframe.cpp:559
#17 0x0000003c073b0deb in QGraphicsView::viewportEvent (this=<value optimized out>, event=<value optimized out>) at graphicsview/qgraphicsview.cpp:2919
#18 0x000000308eb50fb8 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=<value optimized out>, receiver=<value optimized out>, event=<value optimized out>)
    at kernel/qcoreapplication.cpp:726
#19 0x0000003c06dd7fec in QApplicationPrivate::notify_helper (this=<value optimized out>, receiver=<value optimized out>, e=<value optimized out>) at kernel/qapplication.cpp:4061
#20 0x0000003c06de07ca in QApplication::notify (this=<value optimized out>, receiver=<value optimized out>, e=<value optimized out>) at kernel/qapplication.cpp:3767
#21 0x0000003c080240db in KApplication::notify (this=<value optimized out>, receiver=<value optimized out>, event=<value optimized out>) at ../../kdeui/kernel/kapplication.cpp:302
#22 0x000000308eb51c9c in QCoreApplication::notifyInternal (this=<value optimized out>, receiver=<value optimized out>, event=<value optimized out>) at kernel/qcoreapplication.cpp:610
#23 0x0000003c06ddfa78 in QCoreApplication::sendSpontaneousEvent (receiver=<value optimized out>, event=<value optimized out>, alienWidget=<value optimized out>, nativeWidget=<value optimized out>, 
    buttonDown=<value optimized out>, lastMouseReceiver=<value optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:216
#24 QApplicationPrivate::sendMouseEvent (receiver=<value optimized out>, event=<value optimized out>, alienWidget=<value optimized out>, nativeWidget=<value optimized out>, 
    buttonDown=<value optimized out>, lastMouseReceiver=<value optimized out>) at kernel/qapplication.cpp:2924
#25 0x0000003c06e48659 in QETWidget::translateMouseEvent (this=<value optimized out>, event=<value optimized out>) at kernel/qapplication_x11.cpp:4411
#26 0x0000003c06e4740f in QApplication::x11ProcessEvent (this=<value optimized out>, event=<value optimized out>) at kernel/qapplication_x11.cpp:3552
#27 0x0000003c06e6f76c in x11EventSourceDispatch (s=<value optimized out>, callback=<value optimized out>, user_data=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:146
#28 0x000000308883b12a in g_main_dispatch (context=<value optimized out>) at /tmp/buildd/glib2.0-2.22.2/glib/gmain.c:1960
#29 IA__g_main_context_dispatch (context=<value optimized out>) at /tmp/buildd/glib2.0-2.22.2/glib/gmain.c:2513
#30 0x000000308883e988 in g_main_context_iterate (context=<value optimized out>, block=<value optimized out>, dispatch=<value optimized out>, self=<value optimized out>)
    at /tmp/buildd/glib2.0-2.22.2/glib/gmain.c:2591
#31 0x000000308883eb3c in IA__g_main_context_iteration (context=<value optimized out>, may_block=<value optimized out>) at /tmp/buildd/glib2.0-2.22.2/glib/gmain.c:2654
#32 0x000000308eb7a39c in QEventDispatcherGlib::processEvents (this=<value optimized out>, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:407
#33 0x0000003c06e6ef1f in QGuiEventDispatcherGlib::processEvents (this=<value optimized out>, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#34 0x000000308eb50562 in QEventLoop::processEvents (this=<value optimized out>, flags=<value optimized out>) at kernel/qeventloop.cpp:149
#35 0x000000308eb50934 in QEventLoop::exec (this=<value optimized out>, flags=<value optimized out>) at kernel/qeventloop.cpp:201
#36 0x000000308eb52ba4 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#37 0x0000000000408607 in main (argc=<value optimized out>, argv=<value optimized out>) at ../../korganizer/main.cpp:61