Anyways, I have a problem too.
I think it's a common problem, I remember encountering it in Light Platinum once. Not sure when. In some places, when I turn menu on/kick wild Pokemon's butt/make a trainer eat dirt, game glitches like hell. For example, game's camera going insane, main character's clonning. I have no idea why is it happening. But I pointed out that it happens mostly in places where I put new events.
Hope someone helps.
Hm, do any person events have the "look down" movement type? If so, change it to "No Movement", it makes the ow look down without the glitches.