I dunno - to me 'crazy' indicates someone who is unable to exercise good judgement, and does stuff that most reasonable people wouldn't do. For instance, because I'm crazy in love with my wife, my judgement where she is concerned is colored not by logic, but by emotion.
Insane, to me anyway, conjures images of someone raging and drooling in some Victorian asylum. I suppose you could have an insane craving for pizza, but that's about it.
I don't think we can equate bipolar with crazy or insane. Unless you're bipolar, crazy in love, and have an insane craving for pizza. ;-)