Freezing mouse (possible to switch over to another window)

Press and hold something on your keyboard, like the mouse button to mine or something else. Now press the fullscreen key. While you get the blackscreen stop holding the key/mouse button. Now you're able to switch over to another window by pressing alt+tab(Microsoft Windows), your minecraft client thinks now your holding the key/mouse button.
— Here a tipp/advice: switch over to two another windows. So if you minimize one window you wouldn't get thrown back to minecraft.