Ordinary Day

Yep. They were dancing and talking at the end of Colonial Day -- and she was technically assigned to be his security before that, so it's not a big leap for me that they'd share a shuttle back to Galactica. (I think the party is held on Cloud 9 -- it's too posh-looking for the big G.)

There's a deleted scene wherein Baltar and Kara bump into each other and talk briefly about what went on -- they both say, basically, that they were drunk and that it "Didn't happen. Right? Right." And off they go. So I think they both have big regrets about the whole thing and are perfectly happy to let it go. I'm fairly sure this happens after the poker game, after Baltar's sobered up again. It's only when he's drunk and really broody that the snipe comes out aimed at Kara & Lee. Of course, that's when the worst damage is done...

(queue punch)