Now with your hardware and S.O. i guess its something with Windows 8. Guess that is the problem. Just did a quick search on Google and looks like FXAA+Win8 looks like its not working. My video card is a 560 too, so really this should be something with Win8.
Okay, I see what you mean. Indeed more mentions on Steam based games and FXAA. I blame it on steam cause I hate that virus-like program But okay, seriously: a shame it doesn't work. Think I would like the Vivid setting a lot. Did a DirectX check and all is and looks fine there too.
Oh btw, did just see this now: the whole error message is "Cannot initialise graphics. Directx 10 or 11 support is required."