WE KNOW the equation. Pixar summer movie = smash hit. For the first time, we’re not sure. “Up” may at long last offer a Pixar movie that neither critics nor audiences love, at least all that much. Why? We don’t see that famous Pixar appeal to kids and parents alike. Where “Ratatouille” had the cooking and “Incredibles” had the dysfunctional family humor, “Up” presents us with … a crotchety old man who rigs balloons to his house and sails to The Land of the Lost. This occurs after (we easily forget) “Ratatouille” only opened to $47 million – nothing to sneeze at, but enough to prove the Pixar name doesn’t have the sure-fire earning power the Chattering Classes think. This said, our friend Katey at Cinema Blend is as bullish as ever after having seen parts of the film. Expect controversy in the Summer Movie Challenge as “Up” hits theaters in the last day of May.