This was not actually Kasparov's complaint. He thought there was intervention during the game. He replayed a particular position through a PC and when given an extremely long time to think the PC did not find Deep Blue's move in the same situation. This along with his feeling that the computer 'just wouldn't' find the move made him believe that someone had essentially told Deep Blue to pick an alternate move from the tree creating a man-machine combination. This was not substantiated and seems unlikely considering the Kasparov - Deep Blue matches generated so much publicity even with Kasparov winning. In either case his accusations reflect badly on him since he doesn't have any real evidence. If he hadn't failed to find a draw in one of the games he probably would not have lost the match. Also the blunder in the last game could have been avoided but it seems human fallibility and some point would have done him in no matter what.