I have a similar issue with games like assassins creed 2 , fallout 3 and fallout new vegas for example. In a moment the ps3 memory cache gets full and you will see a slowdown in game and a later crash (that hapend to me) and was fixed by updates, in other cases a re-install of the game solved , other cases was related to change the original HD for a higer one, i don't know what is exact your problem is, but that is my experience.
Hey violentcris, what you said about changing the original hard drive to a bigger one caught my attention, since about a month ago I upgraded my ps3 60gb to a 500GB do you think this might be a part of the problem? How did you fix your ps3 when it did it?
You know man know people with that issue (i don't have the hdd problem) over here are guys that make that job they exchange your HD and if any issue they take care, the only problem i have is a bad install.
I found a place that's charging $100 to replace the entire blu-ray drive with a new one and they offer a 90 day warranty. Also the guy told me it would be done in 2-3 hours while other shops have to keep it for days. I figured I'll take it there since most blu ray drives i've seen online cost between $80-$100 and I would have to wait for a week to get it. I'll let you guys know how it turns thanks for everything!
. Also make sure the Blu ray drive is the right one for your PS3. 
