It seems that depends on the umpire's whim, judging by recent evidence. I'd have said that because the infield fly rule was called the batter was out either way, BUT I believe they called the runner at second out for interference. Which raises the question, doesn't the runner have the right to go back to the bag unimpeded by the fielder. Also raises the question, does the runner have to tag up before trying to advance? I know the rule says something about the runners "advancing at their own risk", but I'm not sure about the exact mechanics of it. Personally, I think the rule should be changed to making the ball dead once the infield fly rule is called and having the runners simply stay where they were.