There is no doubt this is a weak spot in her campaign that her staff has been ineffective in protecting.
Obama's opposition to the war, and the absence of this kind of thing in his record is a serious factor in his success to date.
That being said, that a clever and competent staff in the Clinton camp, and they are well connected to the levers of power in the Democratic party. Don't count this woman out of the nomination until the final gavel falls at the convention.