Heath Ledger was looking somber at the Venice film fest today following his split from longtime girlfriend Michelle Williams. At a news conference Tuesday afternoon promoting his new film I'm Not There, an witness described the actor as very quiet while fielding questions from reporters. "He kept his head down a lot and I think he was hoping not to be asked too much," said the onlooker. "He had his hat tipped a little low and didn't really make eye contact with anyone. You could tell he didn't want to be there." The press were only allowed to ask questions about the movie, and didn't question the actor about his recent breakup. "Heath clearly had a lot going on in his head," said the source. "Sometimes he was just staring off to the side, clearly in his own world."