I just got an HD 4870 and was having the no FSAA problem as well on catalyst 9.2. What fixed it was setting FSAA, Depth of Field, Bloom, Water Effects, and Desaturation all to off, and then set AA to 4x via the Catalyst Control. It was frustrating, though, since AA would not turn on if any of those settings was enabled to any extent on the ingame menu.