I am having this same issue - I've disabled antialiasing through the NVidia inspector, the NVidia 3D Control Panel Settings, Skyrim.ini, SkyrimPrefs.ini - nothing seems to be working! My VC is a GTX 570. I'm able to enable DoF, Bloom, and SunRays but I cannot enable Ambient Occlusion. I have also tried using SMAA as a proxy d3d9 source for SkyRealism ENB but I'm getting no love. Any ideas?