Looks related to bug 333595. Is this a multiple screen setup?

(In reply to comment #1)
> Looks related to bug 333595. Is this a multiple screen setup?

Yes it is multiple screen set-up, I will try to reproduce on a single screen setup. 

It really seems stochastic for when it happens or it might be related to some kwidget running in the background giving hidden notifications or something. I have knotes, klipper, korganizer reminder deamon and a couple of others.

I cannot reproduce bug 333595 with the directives given.
For instance my Alt-tab is working after closing 1 of 2 windows open, etc.

can you also please attach the output of
   qdbus-qt4 org.kde.kwin /KWin supportInformation

method QStringList org.kde.KWin.activeEffects()
method Q_NOREPLY void org.kde.KWin.cascadeDesktop()
method void org.kde.KWin.circulateDesktopApplications()
method bool org.kde.KWin.compositingActive()
method QString org.kde.KWin.compositingNotPossibleReason()
method bool org.kde.KWin.compositingPossible()
signal void org.kde.KWin.compositingToggled(bool active)
method QString org.kde.KWin.compositingType()
method int org.kde.KWin.currentDesktop()
method QDBusRawType::ai org.kde.KWin.decorationSupportedColors()
method void org.kde.KWin.doNotManage(QString name)
method Q_NOREPLY void org.kde.KWin.killWindow()
method QStringList org.kde.KWin.listOfEffects()
method void org.kde.KWin.loadEffect(QString name)
method QStringList org.kde.KWin.loadedEffects()
method void org.kde.KWin.nextDesktop()
method bool org.kde.KWin.openGLIsBroken()
method void org.kde.KWin.previousDesktop()
method Q_NOREPLY void org.kde.KWin.reconfigure()
method void org.kde.KWin.reconfigureEffect(QString name)
signal void org.kde.KWin.reinitCompositing()
signal void org.kde.KWin.reloadConfig()
method bool org.kde.KWin.setCurrentDesktop(int desktop)
method void org.kde.KWin.showWindowMenuAt(qlonglong winId, int x, int y)
method bool org.kde.KWin.startActivity(QString)
method bool org.kde.KWin.stopActivity(QString)
method QString org.kde.KWin.supportInformation()
method QString org.kde.KWin.supportInformationForEffect(QString name)
method Q_NOREPLY void org.kde.KWin.toggleCompositing()
method void org.kde.KWin.toggleEffect(QString name)
method Q_NOREPLY void org.kde.KWin.unclutterDesktop()
method void org.kde.KWin.unloadEffect(QString name)
method bool org.kde.KWin.waitForCompositingSetup()
method QDBusVariant org.freedesktop.DBus.Properties.Get(QString interface_name, QString property_name)
method QVariantMap org.freedesktop.DBus.Properties.GetAll(QString interface_name)
method void org.freedesktop.DBus.Properties.Set(QString interface_name, QString property_name, QDBusVariant value)
method QString org.freedesktop.DBus.Introspectable.Introspect()
method QString org.freedesktop.DBus.Peer.GetMachineId()
method void org.freedesktop.DBus.Peer.Ping()

entire "qdbus-qt4 org.kde.kwin /KWin supportInformation", please - we know the interfaces ;-)

lol sorry about this, my bad.

http://goo.gl/2GRy3M

Screens
=======
Multi-Head: no
Active screen follows mouse:  no
Number of Screens: 2
Screen 0 Geometry: 0,0,1920x1080
Screen 1 Geometry: 1920,0,1920x1080

focusPolicy: 0
nextFocusPrefersMouse: false
separateScreenFocus: false
focusPolicyIsReasonable: true
focusStealingPreventionLevel: 1

-----------

It's NOT a multihead issue, normal click-to-focus and default focus stealing prevention.

From your description, it seems that the notifications are the culprit?
Can you try working w/o plasma-desktop or the notification plasmoid for a while and see whether this still happens (to confirm the idea)

   kquitapp plasma-desktop

will shut down the entire desktop (wallpaper, plasmoids and stuff, but not the window manager -alt+tab- or other applications)

   plasma-desktop

will restart it (both can be run from Alt+F2, but i'd keep a konsole open ;-)

It seems to solve the problem !

Is there a log somewhere for the kapps running  I can look at ? 

I could also try to stop them 1 at a time, to see if I can pinpoint the guilty one.

"it" being to shutdown plasma-desktop?

That would be bug #318350, also see bug #311467 and bug #327438

*** This bug has been marked as a duplicate of bug 318350 ***