Question in real-life psychology...

(Not that psychology isn't based on real life, but I'm weird and prefer to trust what my friends think than what psychologists (who aren't my friends, as I suppose those sets will eventually have a nontrivial intersection) think. :)) This came up in real life, but I'm not too worried about it, though I was for a bit--mostly, I'm just confused, and would like to know if there's some kind of self-improvement to be had, or just better grokking power.

Has anyone ever come across the phenomenon in which one meets person A meets person B and they start hanging out, then just when person A starts to think people A and B can become good friends (because B has shown definite signs of interest in doing so), person B starts acting strange, and it becomes clear that person B doesn't like person A at all--and then, moreover, is less willing to interact with person A than with a stranger? I've been person A, and I know some of you (though I don't know if you're /alive/, ahem) have too, but I don't think I've been person B, so I'd like to hear both sides. Can anyone account for this phenomenon? I guess this is question number 3.

As for me, I'm wet--and very glad that I nicked those terrycloth slippers from the Japan Airlines plane (hey, they were for us to use and came with a packet, I think the idea is they're disposable) because that way I don't have to try to get my socks off and smell stuff. It started raining just before I left the building--I protected my books inside my backpack with my jacket, though...[opens bag] yes, they're dry. :)