PS3 Screen goes black and freezes after starting game?

2 days ago I got a problem with my ps3. Whenever I start littlebigplanet my screen freezes black and I am forced to restart the game. Sometimes it gets stuck at the "Important Info" screen. Whenever I press the PS on during a game it freezes and loads non-stop. If I go back to gameplay its all dark and opaque and I cant do anything. Resistance 2 doesnt freeze after I start it but it does freeze when I press the PS on during gameplay. Whats the problem? I have the right inputs and everything.