During multi user online play if one person was killed you get the message you cannot revive while allie is in combat, however the allie is not in combat. This happened consistantly with us in Chapter 1 Chronicals of Blood. No matter how long you stood there the other peson did not get the ability to respawn, God forbid if both of you were killed because you just lay there forever. Only way to get respawned was to go back to main menu and reload the game.