Vladimir Kramnik, who otherwise played an excellent and aggressive game against Deep Fritz today, blundered in Game 2 at move 34 by not seeing a very obvious mate in one.
Kramnik played black and obliged Fritz with a Queen's Gambit Accepted. He forced much of the play early on, with Deep Fritz eventually rebounding to equalize the board. Had Kramnik seen Fritz's threat at move 34 the game would have most likely ended in a draw.
In the diagram to the right, Kramnik moves his queen to E3 threatening a mate of his own and assumes an exchange of queens. At this time he's completely oblivious to the threat in the far right corner, as Fritz's next move is queen to H7: mate.
Interestingly, even one commentator missed the mate-in-one threat. After making his ill-fated move, Kramnik was about to stand-up and take a break when Fritz quickly calculated the checkmate. Kramnik put his hand to his forehead in shocked disbelief.
Blunders happen, even among the grandmasters.
But not computers.