i believe the checkunit command was overwrited in deadson's m2server.exe (i have the same error - with untouched npcs from the original files).
edit by wittin
also, 'benjamin' seems to be causing alot of these error's delete the npc, it isnt an original npc anyhow.
'Daron/Baron' (cant really see) seems to be causing an error - and is not an original npc, as does 'rarez'
-Wittin