Julia Roberts fans take note: The Pretty Woman doesn't have six movies opening this month. It's just that her new film has had six titles. The Aug. 4 release, originally Grace Under Pressure, was retitled Sisters, The Kings of Carolina, Game of Love, Power of Love, and, finally, Something to Talk About. According to director Lasse Hallstrom, Warner Bros. changed the name when it discovered that Grace Under Pressure was registered for an upcoming Rosie Perez comedy. ''We've been searching for the perfect title,'' says Hallstrom, who adds that test marketing prompted the studio to go with Something to Talk About, after the Bonnie Raitt tune heard on the soundtrack. The deciding factor? ''It doesn't hurt that it's a popular song with [the film's] target audience,'' says Warner advertising chief Rob Friedman.