Place sugar and cream cheese in a large bowl; beat with a mixer at medium speed until light and fluffy. Add banana and eggs; beat until well blended. Add the baking mix and walnuts, and stir just until moist.
Pour batter into a 9-inch loaf pan coated with cooking spray; bake at 350° for 45 minutes. Tent bread with foil, and bake an additional 15 minutes.or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on a wire rack; remove from pan. Cool completely on wire rack.