My PS3 will suddenly turn itself off (green light > yellow light > a few times red light with bleeping sound) when playing AC3 or Call of Duty 3, it started switching itself off after 10 to 20 minute of gameplay, I don't think it has overheated.

The strange thing is, this only happen to certain game, such as AC3 or Call of Duty 3, I've tried God of War 3 for 2 hours, no problem at all. I also tried deleting the game data and reinstall it, the problem still occur. Help me.

My PS3 is the fat 80gb Singapore version.