Application: umbrello (2.14.3)
KDE Platform Version: 4.14.3 (Compiled from sources)
Qt Version: 4.8.6
Operating System: Linux 4.0.5-1-ARCH x86_64
Distribution (Platform): Archlinux Packages

-- Information about the crash:
The document was acting strangely up until this point: dragging about 5 class boxes around at once didn't maintain relative distances between some of them, and dragging class relationship labels either occasionally didn't work at all or they appeared to 'jump' to some x or y off the visible section of the map. 

Umbrello then crashed upon clicking and attempting to drag the 'frozen' label of one of these relationships.

The crash can be reproduced every time.

-- Backtrace:
Application: Umbrello UML Modeller (umbrello), signal: Segmentation fault
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[KCrash Handler]
#6  0x00007fbc98d9f900 in QGraphicsItem::setPos(QPointF const&) () from /usr/pkg/qt4/lib/libQtGui.so.4
#7  0x000000000060f64e in Uml::CmdMoveWidget::redo (this=0x1a529d0) at /local/scratch/pkgsrc/devel/umbrello/work.debretts/umbrello-4.14.3/umbrello/cmds/widget/cmd_moveWidget.cpp:39
#8  0x00007fbc98e27577 in QUndoStack::push(QUndoCommand*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#9  0x00000000006dc5dc in UMLApp::executeCommand (this=0x189a990, cmd=cmd@entry=0x1a529d0) at /local/scratch/pkgsrc/devel/umbrello/work.debretts/umbrello-4.14.3/umbrello/uml.cpp:3232
#10 0x000000000065819b in UMLWidget::mouseReleaseEvent (this=0x22a2700, event=<optimized out>) at /local/scratch/pkgsrc/devel/umbrello/work.debretts/umbrello-4.14.3/umbrello/widgets/umlwidget.cpp:562
#11 0x00000000006d236d in ToolBarState::mouseRelease (this=0x226f4a0, ome=<optimized out>) at /local/scratch/pkgsrc/devel/umbrello/work.debretts/umbrello-4.14.3/umbrello/toolbarstate.cpp:121
#12 0x00007fbc98dd51bf in QGraphicsScene::event(QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#13 0x00007fbc987e8ebc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#14 0x00007fbc987ef99c in QApplication::notify(QObject*, QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#15 0x00007fbc99f1113a in KApplication::notify (this=0x7fff5af4d2b0, receiver=0x226ed50, event=0x7fff5af4c530) at /local/scratch/pkgsrc/x11/kdelibs4/work.debretts/kdelibs-4.14.3/kdeui/kernel/kapplication.cpp:311
#16 0x00007fbc9817679d in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/pkg/qt4/lib/libQtCore.so.4
#17 0x00007fbc98debfdf in QGraphicsView::mouseReleaseEvent(QMouseEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#18 0x00000000007305e3 in UMLView::mouseReleaseEvent (this=0x22599c0, event=<optimized out>) at /local/scratch/pkgsrc/devel/umbrello/work.debretts/umbrello-4.14.3/umbrello/umlview.cpp:251
#19 0x00007fbc98839430 in QWidget::event(QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#20 0x00007fbc98bdd95e in QFrame::event(QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#21 0x00007fbc98deca2f in QGraphicsView::viewportEvent(QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#22 0x00007fbc98176906 in QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) () from /usr/pkg/qt4/lib/libQtCore.so.4
#23 0x00007fbc987e8e9c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#24 0x00007fbc987efb03 in QApplication::notify(QObject*, QEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#25 0x00007fbc99f1113a in KApplication::notify (this=0x7fff5af4d2b0, receiver=0x226e8d0, event=0x7fff5af4cb10) at /local/scratch/pkgsrc/x11/kdelibs4/work.debretts/kdelibs-4.14.3/kdeui/kernel/kapplication.cpp:311
#26 0x00007fbc9817679d in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/pkg/qt4/lib/libQtCore.so.4
#27 0x00007fbc987ef19d in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) () from /usr/pkg/qt4/lib/libQtGui.so.4
#28 0x00007fbc9886395d in QETWidget::translateMouseEvent(_XEvent const*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#29 0x00007fbc98861c33 in QApplication::x11ProcessEvent(_XEvent*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#30 0x00007fbc988895e2 in x11EventSourceDispatch(_GSource*, int (*)(void*), void*) () from /usr/pkg/qt4/lib/libQtGui.so.4
#31 0x00007fbc940a5817 in g_main_context_dispatch () from /usr/pkg/lib/libglib-2.0.so.0
#32 0x00007fbc940a5a48 in g_main_context_iterate.isra () from /usr/pkg/lib/libglib-2.0.so.0
#33 0x00007fbc940a5aec in g_main_context_iteration () from /usr/pkg/lib/libglib-2.0.so.0
#34 0x00007fbc981a4834 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/pkg/qt4/lib/libQtCore.so.4
#35 0x00007fbc98889686 in QGuiEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/pkg/qt4/lib/libQtGui.so.4
#36 0x00007fbc98175151 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/pkg/qt4/lib/libQtCore.so.4
#37 0x00007fbc98175465 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/pkg/qt4/lib/libQtCore.so.4
#38 0x00007fbc9817aa69 in QCoreApplication::exec() () from /usr/pkg/qt4/lib/libQtCore.so.4
#39 0x0000000000439c9a in main (argc=<optimized out>, argv=<optimized out>) at /local/scratch/pkgsrc/devel/umbrello/work.debretts/umbrello-4.14.3/umbrello/main.cpp:123

Reported using DrKonqi