Many of us, my self included, gave up refreshing their browsers when we were informed that the sale was postponed. Just because we received word that it wasn't going to happen we should be penalized for it? The reason people were successful later was due to the fact that word was spreading that the sale was postponed thus the load on the servers wasn't as great with less people refreshing. Had we known that this would have happened I'm sure we wouldn't have stopped refreshing.
Figure out what time the first notice of the sale postponement was announced, honor any sales before that time and refund sales after said time.
You can't announce a postponement and then continue to sell the poster.