Probably you have wrong creature type in RME creatures.xml and it's saved as NPC instead of monster. Go to RME folder, data/yourclienthere/creatures.xml, search for Cobra and Orc Berserker, and change both types from npc to monster.
or
go to your server data/world/spawnfile.xml search for
npc name="Cobra" and
npc name="Orc Berserker" and change to
monster name="Cobra" and
monster name="Orc Berserker".
Next time look if you're adding NPC's or monsters.
If these wont solve your problem then I have no idea.