When ending the session, logging out or rebooting, a kcrash window is displayed. Here's the backtrace:
Application: plasma-desktop (0.4)
KDE Platform Version: 4.7.00 (4.7.0)
Qt Version: 4.7.3
Operating System: Linux 3.0.0-desktop-0.rc7.5.1.mga2 x86_64
Distribution: "Mageia Cauldron"

-- Backtrace:
Application: Plasma Desktop Shell (kdeinit4), signal: Segmentation fault
[KCrash Handler]
#6  0x00000000023ded08 in ?? ()
#7  0x00007f31c8ef5d86 in TaskGroupItem::~TaskGroupItem (this=0x2dc5ff0, __in_chrg=<value optimized out>) at /usr/src/debug/kde-workspace-4.7.0/plasma/desktop/applets/tasks/taskgroupitem.cpp:82
#8  0x00007f31c8ef5e39 in TaskGroupItem::~TaskGroupItem (this=0x2dc5ff0, __in_chrg=<value optimized out>) at /usr/src/debug/kde-workspace-4.7.0/plasma/desktop/applets/tasks/taskgroupitem.cpp:83
#9  0x00007f31dfc848e8 in QObject::event (this=0x2dc5ff0, e=<value optimized out>) at kernel/qobject.cpp:1200
#10 0x00007f31df43842b in QGraphicsWidget::event (this=0x2dc5ff0, event=0x2dbdc90) at graphicsview/qgraphicswidget.cpp:1423
#11 0x00007f31dee0b954 in QApplicationPrivate::notify_helper (this=0x21ebff0, receiver=0x2dc5ff0, e=0x2dbdc90) at kernel/qapplication.cpp:4462
#12 0x00007f31dee1052a in QApplication::notify (this=<value optimized out>, receiver=0x2dc5ff0, e=0x2dbdc90) at kernel/qapplication.cpp:4341
#13 0x00007f31e0a0d016 in KApplication::notify (this=0x21d50b0, receiver=0x2dc5ff0, event=0x2dbdc90) at /usr/src/debug/kdelibs-4.7.0/kdeui/kernel/kapplication.cpp:311
#14 0x00007f31dfc703dc in QCoreApplication::notifyInternal (this=0x21d50b0, receiver=0x2dc5ff0, event=0x2dbdc90) at kernel/qcoreapplication.cpp:731
#15 0x00007f31dfc73be5 in sendEvent (receiver=0x0, event_type=52, data=0x20e9430) at kernel/qcoreapplication.h:215
#16 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=52, data=0x20e9430) at kernel/qcoreapplication.cpp:1372
#17 0x00007f31dfc73ede in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1015
#18 0x00007f31d03d2c0d in kdemain (argc=1, argv=0x2148660) at /usr/src/debug/kde-workspace-4.7.0/plasma/desktop/shell/main.cpp:120
#19 0x0000000000406d39 in launch (argc=1, _name=0x2148628 "/usr/bin/plasma-desktop", args=<value optimized out>, cwd=0x0, envc=<value optimized out>, envs=<value optimized out>, reset_env=false, 
    tty=0x0, avoid_loops=false, startup_id_str=0x40ae4e "0") at /usr/src/debug/kdelibs-4.7.0/kinit/kinit.cpp:734
#20 0x0000000000407940 in handle_launcher_request (sock=<value optimized out>, who=<value optimized out>) at /usr/src/debug/kdelibs-4.7.0/kinit/kinit.cpp:1226
#21 0x0000000000408095 in handle_requests (waitForPid=<value optimized out>) at /usr/src/debug/kdelibs-4.7.0/kinit/kinit.cpp:1419
#22 0x0000000000408ce0 in main (argc=4, argv=0x7fff9b1e3988, envp=0x7fff9b1e39b0) at /usr/src/debug/kdelibs-4.7.0/kinit/kinit.cpp:1907