If you strip away the jargon it's simple, really. There is a 6 game series going on between current men's chess #1 Kramnik and an Intel based computer (not a mainframe) called Deep Fritz. When they met last time, I think it was 4-4 draw. This time around is considered the first time the human starts out as the underdog and may well be the last time this thing is even competitive!
Game 1 was on Saturday and was a draw. In today's game, which seemed a fairly aggressive one to me (others might differ), somewhere at the half-point of the game, Kramnik seemed to have gained a small advantage. As he pushed through with his pieces he failed to notice something very basic: that a particular move by the computer had put him at risk of being one move away from a checkmate. This is an amazing error on the part of such a skilled player!
Unlike Kasparov, I don't find anything bawl-worthy about losing to a computer (perhaps because I have suffered that humiliation many times over, or perhaps because I think humans are dumber than computers ;-)), but nevertheless, it was dismaying to watch someone throw away a crucial game like that.
--ravi