heya,
nah, I wouldn't know without both the config file and nightmare profile
you can use rbe debug command to see what's going on
I'm off to bed so I won't be able to help until later
the difficulty might not be set in the profile, profile enabled might be false, height setting could be wrong somewhere, protection radius might be wrong (should be 50 by default), if Include PVP is false and Allow PVP is true in the profile then it won't spawn, etc
lots of ways to break it!
definitely try rbe debug. that's what it's there for