The Clues Challenge (Nancy Drew Series #163)

Dangerous pranks ice over an outdoor treasure hunt -- and Nancy has to melt down the culprit!
Nancy and her friend George are visiting Emerson College, courtesy of Nancy's boyfriend, Ned. His fraternity is eager to win the Clues Challenge, an athletic treasure hunt sponsored by a local sporting goods store, so the girls join Ned's team. But accidents, dirty tricks, and computer warnings threaten to shut down the whole event.
Nancy suspects that someone has cheated by giving out the answer...