Havok was breifly in X-Factor with Polaris after they returned from space. It didn't go well (since Maddrox is team leader and Havok was trying to butt in). Storywise, I think he left after it was obvious it wouldn't work out, and later (after AvsX) Cap recurited him. Polaris stayed with X-Factor. This all happened very far into this current X-Factor's run, most of it Polaris and Havok were in space (and comic book limbo) and had nothing to do with this version of X-Factor until their return from space.