Check your graphic card settings to check if you aren't forcing the drivers to apply AFx16 and AAx4.
Some people expecting max quality from their graphic card go and make the drivers force some settings that afterwards the aplication doesnt realy "like".
At least in the ATI radeon control panel you can force some settings on the game, while its probably preferable to leave it at "aplication setting" where the in-game menu you can control the details at will.
