I believe that this is just a parliamentary procedure thing. You make a motion that a group accept someone by unanimous consent. If someone in the group wants an actual vote to be taken, for whatever reason, this motion is defeated and then a motion for a vote is made.
From the news account below, it appears that someone is trying to put a spin on this.
“WASHINGTON:A spokesman for Senate Majority Leader Harry Reid says Hillary Rodham Clinton will not be confirmed as secretary of state Tuesday because of a single senator’s objection. Reid spokesman Jim Manley said Republican John Cornyn of Texas has indicated he will block a move to confirm Clinton by an unanimous floor vote later in the day.”