I would guess that you added a Method of Death somewhere in middle of the table of them, which changed all the numberics of the death methods, offsetting all those below the addition. Death messages are sent to the client as a numeric, and the client displays the death message for the corresponding MoD. If you mess with them on the server within the original range, it won't be correct anymore.
If you don't remember adding a MoD, you probably did it for/during !slap.