Hmmmmm. Never really thought about it.

i think everytime she asked him to get together or do something together he said no
remember? the last scene in "the merger"

Well, when he got back from Stamford he turned down her offer to have coffee because he was "kind of seeing someone" (Karen).

I think the real rejection happened on Beach Day. Pam admitted her feelings and then Jim told her they would always be "friends." It wasn't as obvious a rejection as when Pam did it to him, but it was still a rejection.

Yeah, in the Merger, Pam says something like, "So, when do I get to hear everything? Are you still unpacking? Do you want to go out for a cup of coffee?" Then Jim turns her down... sort of.

Yeah. chel1395 is right. Jim was cold towards Pam all season. He like rejected a friendly outing in the Merger when Pam asked him out for coffee. But the real rejection was in Beach Day. Remember how Pam said in The Job, "he just basically told me that he missed my friendship too and i would always mean a lot to him and i understand where he's coming from"? So Jim basically gave her a rejection

yeah, i thought about this, too.
i think she meant when he told her he couldnt go out for coffee...but maybe it was beach day.

or whenever he was making fun of her job and saying she should go for the art thing, that was being pretty mean. I guess it was a lot of cold acts. and the coffee thing.

when he said she should go for the art thing
he was being more supportive than roy and that was very nice from jim

I think it's the sense in everything he did (Or for that matter didn't do) since he had come back from the Stamford branch. Everything she had mentioned on the Beach Day episode...