How is it possible that my Macbook Pro with a failed logic board works just fine?
I've heard of a logic board "limbo state" where it passes in and out of working. It is broken, but it's letting you use it until it decides to die altogether. You may as well get all the life you can out of it, but don't depend on it to heavily.

I can't find confirmation of this, but I know I've heard stories of it before. Can anyone confirm?