Louise (Laura Linney) is 39, an admissions officer at Columbia's graduate school of arts and maintaining a friendly relationship with her ex, physics professor Peter (Gabriel Byrne). Into her dull life comes young F. Scott (Topher Grace), an admissions candidate who more than resembles Louise's long-dead high school sweetheart. A relationship ensues -- and soon has Louise re-examining her relationships, both past and present. Director Dylan Kidd (Roger Dodger) adapted Helen Schulman's novel (Schulman co-wrote the screenplay with Kidd), and at times the film's rhythms seem off: The burgeoning romance seems more languid than fevered, and the conclusion gets cluttered with a series of explanations, while never fully resolving the story's earlier conceit that F. Scott is a near re-incarnation of the old love. Still, P.S. is ably acted: Byrne and Linney affect their calling cards -- shaggily roguish and quietly heartbroken, respectively -- with That '70s Show's Grace showing real promise. Starts Wed., Nov. 24. Oaks