PARIS — For a decade, the French Open has presented more problems for Serena Williams than any of the other Grand Slam tournaments. Her collection of 15 major championships includes five from Wimbledon, five from the Australian Open, four from the U.S. Open ... and one from Roland Garros. Ever since she beat her sister in the 2002 final in Paris, starting a run of four consecutive titles at tennis' most important events, one thing or another has prevented Williams from a second French Open trophy.