Steps to reproduce:

Run the attached sample as applet

- Hold the mouse over the button
- Result: The popup never hides again, resulting into:

java.lang.IllegalStateException: The window must be focused when calling grabFocus()
at com.sun.glass.ui.Window.grabFocus(Unknown Source)
at com.sun.javafx.tk.quantum.WindowStage.grabFocus(Unknown Source)
at javafx.stage.Window.increaseFocusGrabCounter(Unknown Source)
at javafx.stage.PopupWindow.impl_visibleChanged(Unknown Source)
at javafx.stage.Window$10.invalidated(Unknown Source)
at javafx.beans.property.BooleanPropertyBase.markInvalid(Unknown Source)
at javafx.beans.property.BooleanPropertyBase.set(Unknown Source)
at javafx.stage.Window.setShowing(Unknown Source)
at javafx.stage.Window.show(Unknown Source)
at javafx.stage.PopupWindow.showImpl(Unknown Source)
at javafx.stage.PopupWindow.show(Unknown Source)
at javafx.scene.control.Tooltip$TooltipBehavior$1.handle(Unknown Source)
at javafx.scene.control.Tooltip$TooltipBehavior$1.handle(Unknown Source)
at javafx.animation.Animation.impl_finished(Unknown Source)
at com.sun.scenario.animation.shared.SingleLoopClipEnvelope.timePulse(Unknown Source)
at javafx.animation.Animation.impl_timePulse(Unknown Source)
at com.sun.scenario.animation.shared.AnimationPulseReceiver.timePulse(Unknown Source)
at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(Unknown Source)
at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit$9.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(Unknown Source)
at com.sun.glass.ui.win.WinApplication$2$1.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
preloader: Stop progressCheck thread