Therapist Paul Weston, a human-shaped cloud who grumbles with the low thunder of the maladjusted, has drifted back for a gripping new season of HBO's In Treatment (Oct. 25). Gabriel Byrne plays the part flawlessly, and he's up against two especially rewarding talents. Debra Winger-splendidly tough-is a new patient, an actress with some complicated sister issues. And Amy Ryan is Paul's watchful new therapist. He underestimates her until she practically KOs him with one clear, simple observation.