If you are experiencing freezes in multiple games, that is generally a hardware problem. Most commonly, a problem with the hard disk. Contrary to popular belief, this isn't caused by the PS3 System software. The PS3 gives full control of the hardware to PS3 games while they are running, so the System software can't cause the game to freeze. A defect in the game can cause it to freeze, but if it happens in multiple games, then that is almost always a hardware problem. You may need to replace your PS3 hard disk drive.