I had this too. It usually happens when they get up from bed, suddenly their mood is bad, even if they have some good moodlets. This is really annoying trying to get your sim a famous actor...
Edit: I cleared my game from all custom content. It seems to not have solved the mood problem, which is incredibly great. (But now everything looks kind of boring to me. Not used to play without downloads any more.) And now my sim constantly changes to formal wear. I mean, she does this at home. The NL-patch is more like a NL-Bug, right?