Ps3 Graphs Problem end in blackscreen

Hi, Im playing on ps3 since it came out and my graphics bugs. Let me explain whats happening. It flash and sparkle multicolor everywhere in the screen, its really annoying. Then a black screen arrived, unable me to see anything. Players name and monsters name still appear, i can continu to move, accepting quest, completing quest, anything works fine excepts my graphics. I have to log out and log in to have a new view, but it hold like 5 min then graphs continue to jump and flash then black screen comes again! I tried many things like re-installing the game, remove USB connected to ps3 like the keyboard, i tried to enable javascript in the ps3 browser, i even tried to restore ps3 file system by holding the ps3 buttom 6 seconds twice! it said that the content on the hardrive was corrupted and it will be restore.i dont know what to do please help me! thank you :)