variety of games -same? My 4 year old pS3 has started "freezing up" after about 30-45 minutes of gameplay.Upon restart, system often does not even recognize disc that is inside machine. Tried variety of games -same. I'm guessing that it is either a laser tracking issue, or a heat dissipation issue. I have tried to clear away both side of unit to maimize ventilation. Discs are spotless and scratch-free. SInce it is well out of warranty, any ideas on what to try next? I would even crack it open to vac inside if dust buildup mght be the culprit. Your thoughts?