I think whatever caused Clark to scream "Noooo!" is the shock thearpy I've been talking about.
That'll do it for him.
I've been wondering what Lieta just said, too.
She didn't believe Lana when she told her Clark did love her. Would she believe Clark?
Particularly if she didn't witness his reaction to above event?
I still maintain her letting Clark go is about selfless love from her perception. Objectively speaking, it isn't what she should be doing. She should at least wait for Clark to decide what he wants. But that isn't an option from Lois's POV. Like Carol said, they had already decided they would get a divorce back at the beginning. She's accepted that. She believes letting him go is the best thing she could do.
BUT - as much as it is selfless love from her POV, there is a lot of defense mechinism there as well. That's why she brings up the divorce first. She's not willing to wait and have Clark bring it up. She's preparing her heart early. It's that same defense mechinism that refuses to believe Lana's speech and to wonder why Clark does some of the things he does. (Out of love?)
So, given that that is the case, would she believe Clark if he came to her and said, "I don't want a divorce. I am in love with you."
I wonder if "Unanswered Prayers" is about Clark CONVINCING Lois he is in love with her.