I'm gonna have to persist on this topic and point out a few things:
i) 4x might have been the only one's that "worked," but forcing higher AA settings in NCP would effect presentation, if not in IQ then it would slow down framerates. I distinctly remember this occurring.
ii) Other Games. Forget that I said anything about HL2 for a moment. I used to be able to force AA in Oblivion, and also recently Mass Effect (I know UR3 engine doesn't support AA but I could force it anyway, so don't belabor that point). I can't anymore. I've tried every trick I can think of - renaming .exes, supersampling, AA compatibility modes - nada. It seems to not even want to work in games that offically support high-AA modes, the later HL2s and Assassin's Creed, though I've yet to experiment too much in this area.
Frustrated at the inability to do make any headway I went ahead last night to do a fresh re-install of everything, thinking nHancer (PoS that it is) had screwed up some tucked-away file that borked my whole system. I'm still experiencing the same lack of control through NCP or nHancer.
My options left, that I can see at least, are some Windows update that blocks any 'forcing' of DirectX, or the June DX update itself throwing a fit. I need to do more testing to figure out which.