One day my Samsung Galaxy Tab 7.0 turned off, and I tried holding down the power and volume buttons. It said it needed to download a custom OS or press down on the volume button for restart. Every time I go to restart it just stays at the "Samsung" screen and when I go to download, it will just stay on the screen of the Android character. It says it's downloading, but it will just stay like that until it turns off. Please help.