My guess is this: If you click any controls in an area of the screen controlled by a plugin (such as Silverlight or Flash), the plugin will take the focus and typically continue to intercept keyboard actions. Usually, clicking a blank area of the page will return the focus to the browser itself, but sometimes this doesn't work and you need to use the mouse to change tabs and change back in order to regain control. Or if you use the Windows shortcut Alt+Tab to change to a different window and then Alt+Tab back to Netflix, that might also work (and avoids having to use the mouse). Does that help at all?