Ok, how is it freezing up? As in you have to reset the console from the back because the controller and screen won't do anything? Or is it the game freezes for maybe 2 seconds then goes back to normal? I occasionally get both of that but it's not frequent at all, like a few times a year. Even so it doesn't bother me too much because of checkpoints etc.
Also, what model is your PS3? Is it a 60GB, 80GB etc. Is your PS3 well ventilated and does it get hot very fast? Try cleaning your PS3 THOROUGHLY. Blow in all the vents, clean of all the dust with a moist towel etc.
Forgive me sir, it's been an honour.