         if (contentGroupProps)
         {
             contentGroup.includeInLayout = contentGroupProps.start.includeInLayout;
+
+            // The default action bar hide and show animation will animate the width and height
+            // of the navigator's contentGroup.  If the explicitWidth or explicitHeight properties
+            // were NaN before the animation, they'll be set to real values by the animation.  As
+            // a result, it is necessary to restore them to NaN so that layout properly sizes these
+            // components. 
+            if (isNaN(contentGroupProps.start.explicitHeight))
+                contentGroup.explicitHeight = NaN;
+            
+            if (isNaN(contentGroupProps.start.explicitWidth))
+                contentGroup.explicitWidth = NaN;
+            
             contentGroupProps = null;
         }
     }

    
    /**
     *  @private
     *  Captures the important animation values of component to use
     *  when animating the actionBar's visiblity.
     *  
     *  @param component The component to capture the values from
     * 
     *  @return Returns an object that contains the properties 
     *  
     *  @langversion 3.0
     *  @playerversion Flash 10
     *  @playerversion AIR 2.5
     *  @productversion Flex 4.5
     */    
    private function captureAnimationValues(component:UIComponent):Object
    {
        var values:Object = {   x:component.x,
                                y:component.y,
                                width:component.width,
                                height:component.height,
                                visible: component.visible,
                                includeInLayout: component.includeInLayout,
                                cacheAsBitmap: component.cacheAsBitmap };
        
        return values;
    }
    
    /**
     *  @private
     *  Creates the effect to play on the contentGroup when the navigator is
     *  generating an animation to play to hide or show the action bar.  This effect
     *  should only target the contentGroup as it will be played in parallel with

                                            createActionBarHideEffect();
                                                
                actionBarVisibilityEffect.addEventListener(EffectEvent.EFFECT_END, 
                                                           visibilityAnimation_effectEndHandler);
                
                actionBarVisibilityEffect.play();
            }
