How to fix crashing on Metal Gear Solid Peace Walker?

I'm using PSP 3000 and using CFW 5.03 Prome3 and 503 Kxploit. I can play Peace walker but when every time there a codec call from Kaz the game freeze and crash my PSP to shut down. So I can't play at all right now every time you want to enter a mission there is always a codec call briefing, and my PSP crash everytime. I tried to use Isotool 1.997 but it don't help a bit... Did anyone have the same problem? I don't have this problem before, during that I have been using CFW 5.03 with no prome 3 on the back. Can I roll back my CFW?