Try making a new user, that is not admin, and log in as only that user. See if the crashing still happens.
This is excellent advice. Sorry, I neglected to recommend it.
Still, I think resetting open firmware is worth trying. I believe actually booting into open firmware and resetting from there does more than a simple PRAM reset. Apple seems to suggest it when PRAM resetting doesn't work, which just might be the case here.