Hi I had the same problem with my iPad 4 and also the screen behaved like a goast and functioned anonymously . I tried so many ways and finally ordered a new digitizer. As I have decided to replace the digitizer, I just tried a final try. Just switched off my iPad and slapped three four times on the led screen with my palm firmly. After that the black spots were vanished and even the goast behavior of the screen also gone and till now it works perfectly! Lol This is what I did and my iPad works 100%. It is up to you to try or not. If any thing goes wrong please don't blame me!