Bukkit

What version of Combat Tag are you using?
5.9.0

What version of Bukkit are you using?
MCPC+ 1.5.2 (I use build 643 and 653, but problem expected in all builds).

Do you have an error log of what happened?
http://pastebin.com/39rxyYjG (the same problem as in plugin Anti-Relog because you're using the same NPC library).

What is your plugin list?
It's not important.

Please provide any additional information below.
My Bukkit version doesn't support player NPC's and I suggest make any MOB (non-agressive or mob target event cancellation) instead of PLAYER NPC. Also you can disguise mob as player via sending that packet to client. Big thx.

MCPC+ is always buggy which is most likely causing this anyway, but try using the instantkill version instead.

Can you made monster version? Optionally this monster can be peaceful (EntityTargetEvent cancellation). This suggestion is extremely easy to release ;)

@Bars96: Go

You could always use the instakill version. I'll look at the possibility of this, but I won't make any promises.

Just as a warning, it will not be for the version you're working with. It will only be for those on the latest version. I don't un-update.