Rock pioneer Joan Jett played a special Saturday night set at the Sundance Film Festival in celebration of "The Runaways," the upcoming film about her '70s L.A. all-girl rock band of the same name that had its festival premiere Sunday night. Kristen Stewart and Dakota Fanning, the film's stars, joined Jett on stage. A private reception sponsored by SPIN, Blackheart Records, Apparition, and FLO TV was held at the Interluxe Lounge just before the show. It was fitting that Jett ignited her set at Park City's Harry O's with "Bad Reputation," one of the biggest hits of her solo career. She followed with her No. 1 charting anthem "I Love Rock 'n' Roll" and her ode to self-loathing, "I Hate Myself for Loving You." The standing-room-only audience joined Jett with boisterous screams and shouts of "Oh!