Two similar-sounding, three-syllable, young-guy-with-a-problem movies are playing at Sundance ’05 — The Chumscrubber and Thumbsucker. And are both about suburban ennui and that line of country. Not to sound harsh or dismissive, but I really don’t want to see a movie about a guy who sucks his thumb. Arie Posin’s Chumscrubber, a Premiere selection about, yes, despair and alienation in an idyllic California ‘burb (is there any other kind?), costars Jamie Bell, Ralph Fiennes, Carrie-Ann Moss, Glenn Close, Allison Janey. Mike Mills’ Thumbsucker, playing in the Dramatic Competition section, is a portrait of addiction but is presumably about something else besides. (Please.) It costars Lou Pucci, Tilda Swinton, Keanu Reeves, Vincent D’Onofrio, Bemjamin Bratt, Vince Vaughn.