1. This trace was with ktorrent-dbg installed.

2. Disabling the statsplugin solved the problem.

3. A new backtrace:

Application: KTorrent (ktorrent), signal SIGSEGV
[Thread debugging using libthread_db enabled]
[New Thread 0x7f4fbaada6f0 (LWP 10593)]
[New Thread 0x41dda950 (LWP 10693)]
[New Thread 0x43dde950 (LWP 10692)]
[New Thread 0x40fdf950 (LWP 10598)]
[KCrash handler]
#5  0x00007f4fb88f9beb in QSortFilterProxyModel::parent ()
   from /usr/lib/libQtGui.so.4
#6  0x00007f4fb88b3085 in QTreeView::indexRowSizeHint ()
   from /usr/lib/libQtGui.so.4
#7  0x00007f4fb88b37b5 in ?? () from /usr/lib/libQtGui.so.4
#8  0x00007f4fb88b87f5 in QTreeView::verticalOffset ()
   from /usr/lib/libQtGui.so.4
#9  0x00007f4fb888417e in ?? () from /usr/lib/libQtGui.so.4
#10 0x00007f4fb845ceaf in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#11 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#12 0x00007f4fb845d18b in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#13 0x00007f4fb845d18b in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#14 0x00007f4fb845d18b in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#15 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#16 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#17 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#18 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#19 0x00007f4fb845d18b in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#20 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#21 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#22 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#23 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#24 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#25 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#26 0x00007f4fb845d18b in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#27 0x00007f4fb845d18b in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#28 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#29 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#30 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#31 0x00007f4fb845d262 in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#32 0x00007f4fb845d18b in QWidgetPrivate::paintSiblingsRecursive ()
   from /usr/lib/libQtGui.so.4
#33 0x00007f4fb845c838 in QWidgetPrivate::drawWidget ()
   from /usr/lib/libQtGui.so.4
#34 0x00007f4fb85b6671 in ?? () from /usr/lib/libQtGui.so.4
#35 0x00007f4fb85b6ad7 in ?? () from /usr/lib/libQtGui.so.4
#36 0x00007f4fb845df65 in QWidget::event () from /usr/lib/libQtGui.so.4
#37 0x00007f4fb8776aab in QMainWindow::event () from /usr/lib/libQtGui.so.4
#38 0x00007f4fb9bc8a88 in KXmlGuiWindow::event (this=0x7fffc2b06a80, 
    ev=0x2ed4a60)
    at /build/buildd/kde4libs-4.1.2/kdeui/xmlgui/kxmlguiwindow.cpp:125
#39 0x00007f4fb840bc3d in QApplicationPrivate::notify_helper ()
   from /usr/lib/libQtGui.so.4
#40 0x00007f4fb84139ea in QApplication::notify () from /usr/lib/libQtGui.so.4
#41 0x00007f4fb9ad0b8b in KApplication::notify (this=0x7fffc2b09bb0, 
    receiver=0x2235f40, event=0xfc33cc0)
    at /build/buildd/kde4libs-4.1.2/kdeui/kernel/kapplication.cpp:311
#42 0x00007f4fb8ee9d61 in QCoreApplication::notifyInternal ()
   from /usr/lib/libQtCore.so.4
#43 0x00007f4fb8eea9fa in QCoreApplicationPrivate::sendPostedEvents ()
   from /usr/lib/libQtCore.so.4
#44 0x00007f4fb8f124d3 in ?? () from /usr/lib/libQtCore.so.4
#45 0x00007f4fb407bd3b in g_main_context_dispatch ()
   from /usr/lib/libglib-2.0.so.0
#46 0x00007f4fb407f50d in ?? () from /usr/lib/libglib-2.0.so.0
#47 0x00007f4fb407f6cb in g_main_context_iteration ()
   from /usr/lib/libglib-2.0.so.0
#48 0x00007f4fb8f1215f in QEventDispatcherGlib::processEvents ()
   from /usr/lib/libQtCore.so.4
#49 0x00007f4fb849da9f in ?? () from /usr/lib/libQtGui.so.4
#50 0x00007f4fb8ee8682 in QEventLoop::processEvents ()
   from /usr/lib/libQtCore.so.4
#51 0x00007f4fb8ee880d in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#52 0x00007f4fb8eeacbd in QCoreApplication::exec ()
   from /usr/lib/libQtCore.so.4
#53 0x0000000000423172 in main (argc=4, argv=0x7fffc2b0a7c8)
    at /build/buildd/ktorrent-3.1.2+dfsg.1/ktorrent/main.cpp:165
#0  0x00007f4fb7043621 in nanosleep () from /lib/libc.so.6