sentences:  Maria Sharapova was unsuccessful in defending her 2006 title, being upset in the third round by 18-year-old Agnieszka Radwańska of Poland.Justine Henin, the runner-up to Sharapova in 2006, won her second US Open title, this year without losing a set.It was the second Grand Slam she won in the year without losing a set, having also won the 2007 French Open earlier in the year.