I wasn't there in person, but I've seen a video of a performance at BAM that was roundly booed by the audience. It was an avant-garde piece called The Birth of a Poet, directed by Richard Foreman, produced in 1985. It was kind of a Brechtian nightmare, set in three periods: ancient Rome, contemporary Iran, and NYC in the near future, after the explosion of a power plant. It was a pretentious mess, and at the end the audience booed loudly. Interestingly, as the actors took their bows the boos quieted down, and some people applauded -- because it wasn't their fault, after all -- but when the curtain call was over, the booing resumed.