Server Lag and Crashing when players leave.

Hey Guys,
I'm having a problem where whenever (Everytime) a player leaves it distributes an error message and my server crashes. I've been having this problem for about two weeks now, but the server use to only crash like once or twice every few days from it - its happened twice today so its gotten worst.
Here is the error message upon the last crash. All players got extreme lag and then the server disconnected them all and wouldent let them rejoin. The Server console responded to commands, as you can see in the logs.
http://pastie.org/3163373

All my plugins are up2date, I use the following plugins on the server;
AntiLogger
BorderGuard
Chatmanager
Essentials (All extras except Chat and Group Manager)
Factions
Founddiamonds
Logblock
mcbans
NoEnderman
NoLagg
Parachute
Pearl of Peace
PEX
STAB
Vault
and WWQ

I went ahead and did a restart on the server with a clean log so you can see plugin versions and any problems that each might have.
http://pastie.org/3163435
http://pastie.org/3163456
(Server has 3gb of ram, never hits above 10% cpu usage, and never gets near using its max ram.)

Any help would be awesome! Thanks ahead of time and if you need any more info be sure and let me know!

 

org.martin.bukkit.npclib.NPCManager$1.run(NPCManager.java:47) <- Figure out which plugin uses this library and update or remove it.

 

Which CB build are you using? A build number is required (for example 1597).

Thanks

 

After talking on the Bukkit Irc some more we came to the conclusion that it was a plugin that regulates NPCS, the only npc plugin this server has is Antipvplogger - and it creates an npc duplicate of that player whenever they leave. Should have been pretty obvious to me that this was what was causing it - Disabled the plugin and I will report in if the server continues to have the problem.

Ive posted this error message on the plugin page - hopefully he can fix it soon as that plugin is pretty awesome.