When i firts turn on my thunderbolt it powers on with the vibrate but i dont get no screen till the home back settings and search key tun on and i have to press the sleep button to get the screen showing, also when i try to change the sound setting the screen goes black but i still hear the souns, so i press the wake button again and its back to normal but after a while, the screen is not responsive till i turn it off and back on again so i can use it but thats the only problem does anyone know's what it could be?