It's all tabloid mumbo-jumbo. If they ever hooked up, it was just a one time thing -- I don't think they're actually an "item." I just don't see what the connection there would be, Maria doesn't act mature enough I would think to be someone Andy would be interested in.
And no, I don't think he and Harkleroad ever hooked up. She's married and was engaged before that, and he was dating Mandy Moore back then.