Application: kwin_x11 (5.3.0)

Qt Version: 5.4.1
Operating System: Linux 4.0.4-301.fc22.x86_64 x86_64
Distribution: "Fedora release 22 (Twenty Two)"

-- Information about the crash:
- Unusual behavior I noticed:
1). Login as usual and proceed to coloured screen progress bar gets less than a quarter of the way and login bombs out.
2). Get message saying kwin is unstable - kwin_x11
3). Sometimes progress bar gets nearly halfway then kded5 bombs out instead foe which I have a backtrace but cannot report this bug as system tells me I cannot!

The crash can be reproduced every time.

-- Backtrace:
Application: KWin (kwin_x11), signal: Segmentation fault
Using host libthread_db library "/lib64/libthread_db.so.1".
[KCrash Handler]
#5  0x000000319800e7a0 in xcb_setup_vendor_end () at /lib64/libxcb.so.1
#6  0x000000319800e7f9 in xcb_setup_pixmap_formats_iterator () at /lib64/libxcb.so.1
#7  0x000000319800e839 in xcb_setup_roots_iterator () at /lib64/libxcb.so.1
#8  0x00007f1536d4a587 in NETRootInfo::NETRootInfo(xcb_connection_t*, unsigned int, char const*, QFlags<NET::Property>, QFlags<NET::WindowTypeMask>, QFlags<NET::State>, QFlags<NET::Property2>, QFlags<NET::Action>, int, bool) () at /lib64/libKF5WindowSystem.so.5
#9  0x00007f1537fc7b61 in KWin::RootInfo::create() () at /lib64/libkwin.so.5
#10 0x00007f1537f9fe5c in KWin::Workspace::init() () at /lib64/libkwin.so.5
#11 0x00007f1537fa153b in KWin::Workspace::Workspace(bool) () at /lib64/libkwin.so.5
#12 0x00007f1537fd89ee in KWin::Application::createWorkspace() () at /lib64/libkwin.so.5
#13 0x00007f15383aa16c in QtPrivate::QFunctorSlotObject<KWin::ApplicationX11::performStartup()::{lambda()#2}, 0, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) () at /lib64/libkdeinit5_kwin_x11.so
#14 0x00000031a9eafad7 in QMetaObject::activate(QObject*, int, int, void**) () at /lib64/libQt5Core.so.5
#15 0x00007f1536d2e0bb in KSelectionOwner::Private::claimSucceeded() () at /lib64/libKF5WindowSystem.so.5
#16 0x00007f1536d2e901 in KSelectionOwner::filterEvent(void*) () at /lib64/libKF5WindowSystem.so.5
#17 0x00000031a9e7bc1f in QAbstractEventDispatcher::filterNativeEvent(QByteArray const&, void*, long*) () at /lib64/libQt5Core.so.5
#18 0x00007f152d158f3e in QXcbConnection::handleXcbEvent(xcb_generic_event_t*) () at /usr/lib64/qt5/plugins/platforms/libqxcb.so
#19 0x00007f152d159ff3 in QXcbConnection::processXcbEvents() () at /usr/lib64/qt5/plugins/platforms/libqxcb.so
#20 0x00000031a9eb0b11 in QObject::event(QEvent*) () at /lib64/libQt5Core.so.5
#21 0x00000031ae7527cc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib64/libQt5Widgets.so.5
#22 0x00000031ae757e70 in QApplication::notify(QObject*, QEvent*) () at /lib64/libQt5Widgets.so.5
#23 0x00000031a9e7f24b in QCoreApplication::notifyInternal(QObject*, QEvent*) () at /lib64/libQt5Core.so.5
#24 0x00000031a9e81387 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /lib64/libQt5Core.so.5
#25 0x00000031a9ed3cc2 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /lib64/libQt5Core.so.5
#26 0x00007f152d1ad97d in QUnixEventDispatcherQPA::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/qt5/plugins/platforms/libqxcb.so
#27 0x00000031a9e7ca8a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /lib64/libQt5Core.so.5
#28 0x00000031a9e845fc in QCoreApplication::exec() () at /lib64/libQt5Core.so.5
#29 0x00007f15383ab967 in kdemain () at /lib64/libkdeinit5_kwin_x11.so
#30 0x0000003194c20790 in __libc_start_main () at /lib64/libc.so.6
#31 0x0000000000400bc9 in _start ()

Reported using DrKonqi