That can be ignored.
As is commonly noted, the right of senators to place “holds” on legislative measures and executive and judicial nominations is not formally recognized in the standing rules of the Senate. Holds—or the ability of a single senator to block the majority leader from calling up legislative measures and nominations—arise in the Senate because of the chamber’s reliance on unanimous consent agreements and debatable motions to proceed to schedule business and organize debate on the Senate floor. Lacking a previous question motion, a simple majority is powerless under Senate rules (except under special conditions) to determine whether and when to proceed to consider a measure or matter on the Senate floor. By placing a hold on a measure, a senator is registering his or her intention to object when the majority leader seeks unanimous consent. Although nothing in Senate rules binds either the majority or minority leader to honor his colleagues' holds, such objections typically delay action because leaders are loathe to upset colleagues whose cooperation will be needed in the future. Leaders can ignore holds, but to proceed in face of opposition they would customarily then have to pass a motion to proceed, which is subject to a filibuster.
http://rules.senate.gov/hearings/2003/061703binder.htm
However, filibusters on judicial nominees is also easily overcome, by asking the President of the Senate (Chaney) to rule on the appropriateness of the filibuster as per what the Senate rules are on nominees in the Constitution (basically, the Senate is only to "advise and consent," which is a simple majority).
http://www.npr.org/templates/story/story.php?storyId=4575047
Look at the fourth question for this clarification.