I've always had trouble with the holy phrase "Next Action," and I recently realized why. "Act" refers to the deed, while "action" refers more to the doing, which seems to be why DA calls them Actions in the first place. But Acts are a tiny bit more abstract [in a good way], the little incremental things I want to complete, rather than the way I visualize completing them, which is what Actions are. Kind of like and Act is a mini- or even micro-project. I can get behind acts a lot more than actions. Actions can include spinning my wheels. Acts is like acts in a play, or a legislature. Something whole, even if a small whole, gets done.
See http://www.answers.com/act&r=67, USAGE NOTE.