From what the OP describes, it certainly seems as though the situation could have been managed better. I am wondering though what time of the day he was checking in? All large airports experience peak times, for both check in and TSA security. I have been traveling out of Dulles monthly and have been lucky to not have experienced the OP's situation, possibly due to the fact that I generally check in between 6 and 7 PM when very little is going on.