Wash beans; trim ends and remove strings. Combine beans and water in large saucepan; bring to boil. Cover, reduce heat, and cook 6 to 8 minutes or until crisp-tender; drain and set aside.
Combine sour cream, mayonnaise, vinegar, sugar, salt, pepper and curry powder in large bowl; mix well. Add beans, onion and cucumber; toss gently. Cover and chill 2 to 3 hours.
To serve, arrange lettuce leaves on serving platter. Spoon green bean mixture over lettuce and sprinkle with chopped egg.