I have to agree with th others about the NYSE. Once they get rid of specialists, then you will have better control over your orders. You just got caught up in the closing print. If you have experienced similiar problems with trading NASDAQ or CME, then it is the inefficiency of IB.
Trading at the close is tougher than one thinks, and that goes for all exchanges, even the electronic ones. Example, I submitted a short mini ES put order during the 3:55 to 4:00 PM EST segment of the Globex last week. BTW, the true closing segment of the Globex for mini ES is 4:10-4:15 EST, but it is not as busy. Anyway, I submitted the order, and I get a "pending" notice. I know that I have sufficent margin, so that is not a problem. I waited about 10 minutes before I received a "fill" notation--and I was filled at the limit price I submitted. So, I called technical support to see if my platform was malfunctioning. It wasn't. They had no idea as to why there was a delay. Well, think about this. I submitted my trade on Friday. The 3:55-4:00 PM EST segment of the trading on Friday is probably the busiest, so I assume I still have to "get in line." Fortunately, I was able to place my hedge in time during the 4:05-4:15 segment. Lesson to be learned--probably best to trade a little earlier than the close, and that includes cancellations of roders as well.