Actually, I had the same problem. The edges were all appearing jaggy and I searched google, sent me to this thread (one of the links)... but it didn't solve anything.
Then I thought... what if I actually save the render as an image? What happens then? So I saved the render with "save image" as a JPG. I then opened the JPG and it was all perfectly clean.
So you should try and save the render image and open it and see if it's still present there.