Something is off, way off, with Robert De Niro's acting. He's been working with a vengeance lately, averaging three pictures a year since 1988, and the strain is showing. So far his loyal followers have been content to lavish praise on the emperor's new clothes. Many critics watched him walk through Mad Dog and Glory as Bill Murray's stooge and applauded his zombie act as a dazzling change of pace. Others, myself included, were admittedly impressed by his flashes of showoff brilliance in Awakeni…