Why is my ps vita not wanting to play any game?

For example, i have Call Of Duty Black Ops Declassified and in press the start menu Start button wont work. I also have killzone mercenary, i can get to the game and move a little bit, the button L or R wont work. I also downloaded a demo game from the store and stays like the COD declassified game, on the start menu. Touch wont work on the games either.