java.lang.IllegalStateException: Assertion failed. WindowsAPI is required to be called from AWT thread only, see http://core.netbeans.org/proposals/threading/
        at org.netbeans.core.windows.WindowManagerImpl.assertEventDispatchThreadWeak(WindowManagerImpl.java:1438)
        at org.netbeans.core.windows.WindowManagerImpl.topComponentID(WindowManagerImpl.java:1190)
        at org.openide.windows.WindowManager.findTopComponentID(WindowManager.java:525)
        at org.netbeans.core.windows.model.TopComponentSubModel.getID(TopComponentSubModel.java:365)
        at org.netbeans.core.windows.model.TopComponentSubModel.setSelectedTopComponent(TopComponentSubModel.java:307)
        at org.netbeans.core.windows.model.DefaultModeModel.setSelectedTopComponent(DefaultModeModel.java:171)
        at org.netbeans.core.windows.model.DefaultModel.setModeSelectedTopComponent(DefaultModel.java:612)
        at org.netbeans.core.windows.Central.activateModeTopComponent(Central.java:1694)
        at org.netbeans.core.windows.WindowManagerImpl.topComponentRequestActive(WindowManagerImpl.java:1126)
        at org.openide.windows.TopComponent.requestActive(TopComponent.java:709)
        at org.netbeans.modules.quiz.QuizAction.performAction(QuizAction.java:57)
        at org.netbeans.modules.quiz.Installer.showNotification(Installer.java:118)
        at org.netbeans.modules.quiz.Installer.access$000(Installer.java:64)
        at org.netbeans.modules.quiz.Installer$1.run(Installer.java:94)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)