I'm theorizing that whatever change was made happened during or just after the time they went back in time, as interesting as it would be to speculate how things changed throughout seasons one and two. Of course I'm concerned about why all of their closest friends are so bitterly hostile toward Clark.
Clark's relief that Lois was still alive was so palpable. After "losing" Vicky, I am certain that the thought of losing Lois too was probably more than he could bear. In my opinion, Lois didn't treat his grief with as much respect as it deserved. She told him that everything was okay, but in reality it isn't. They've both lost a lot, even if that is veiled by the mystery they are pursuing.
Elisabeth
