I have two kinds of writers' block. The most common occurs when I am in middle of writing a scene and my mind stops producing useful words. To overcome this, I minimize the text, open my Bridge or Chess program and play for a while. If this doesn't work, I leave the room and try to get my wife to join me for a cup of coffee. The second is more serious and happens when I just can't think of where the plot should go to. The cure, go to a movie or the beach, read a book or just stop trying for a while until inspiration returns.