[greymule]

OK, thanks. This all makes sense. I had no trouble with immediate interference on a ground ball, and if its unintentional and costs the defense a chance at a double play, that's too bad. It was fly balls I couldn't get straight, especially with runners far off their bases.

I will take "no runners may advance" to mean that if the batter or a runner interferes with a fielder attempting to field a batted ball, then anyone not called out goes back to the base at TOP, no matter how far he had advanced before the interference.

It was an ASA case/test play that made me look to OBR for justification for sending runners back:

No outs, Abel on 3B, Baker on 2B, Charles on 1B. Daniels pops up near the 1B line and runs into F3, knocking the ball loose to prevent a double play. Abel has touched home plate prior to the collision.

The answer is:

Dead ball, Daniels is out, Baker is out, Charles is returned to 1B, Abel scores.

Yes, it's true. (I substituted names for R1, R2, etc.)