It very well could be severe complications of old age on Gen IV games. I've had my Platinum do some wacky things that are similar, although I cheated a lot on PT when I was younger. Even so, almost ten years after I stopped hacking, when I do boot it up sometimes it has hiccups.
I would have that same black screen problem sometimes, as a matter of fact - it just occurred once in a while, not really frequently. Sometimes when I rematch NPCs the text glitches. And of course, the odd random freeze. That's mostly it though.