With a all in one it is hard to tell. check your video card connection and make sure it's screwed in tight. Also it could be that your tube is going bad or an easy one to start with is to update your video card driver first.Depending on how old your All in one is, the update video driver is the first thing your should do. After that make sure there are no loose cords in the back of your All in one (if so tighten them up). After that it could be your tube is going bad or your video card connection has come loose. Of course to check the video card you would have to get into your All in one pc and check and see if it has not jarred loose. If the tube is going bad then you will either have to get it fixed or buy another computer. If it is under warranty then Asus will take care of the problem and fix it or send out another one. Mine was going out and they ended up changing the motherboard and tube in the All in One.