Essentially “The Princess Diaries” on ice, Disney’s latest girlie confection stars Michelle Trachtenberg as a science nerd whose physics experiment on the dynamics of figure skating uncovers her raw talent for the sport. The speed at which she becomes a serious contender is ludicrous. The notion that a casual skater, already well beyond the critical formative years for young athletes, could leap to competitive status almost overnight seriously undermines the movie’s credibility. The cast, including Joan Cusack and Kim Cattrall, is likable enough. Rated: G. Rating: 2 out of 4 stars. – David Germain, AP movie writer