Invalid Blocktype Error

EDIT: The problem has been solved. I was mistaken about which plugin was causing the errors. It was ChestLock not Nethrar. ChestLock's save file was referencing blocks that were not lockable block types. Deleted the invalid entries in it's save file and it fixed the errors.

I'm getting the following error when Nethrar tries to load. Now before you ask, the plugin author says it's not his plugin generating the error, but rather bukkit is as a result of his plugin trying to do some processing.

Code:

10:24:11 [SEVERE] Invalid blocktype, Check world name for camerontr;world;268;64;16;,;
10:24:11 [SEVERE] Saving turned off to prevent loss of data
10:24:11 [SEVERE] Invalid blocktype, Check world name for camerontr;world;268;64;10;,;
10:24:11 [SEVERE] Saving turned off to prevent loss of data
10:24:11 [SEVERE] Invalid blocktype, Check world name for camerontr;world;268;64;11;,;
10:24:11 [SEVERE] Saving turned off to prevent loss of data
10:24:11 [SEVERE] Invalid blocktype, Check world name for kEnder242;world;476;60;751;,;
10:24:11 [SEVERE] Saving turned off to prevent loss of data
10:24:11 [SEVERE] Invalid blocktype, Check world name for kEnder242;world;476;60;752;,;
10:24:11 [SEVERE] Saving turned off to prevent loss of data
10:24:11 [SEVERE] Invalid blocktype, Check world name for kEnder242;world;-171;105;1148;,;
10:24:11 [SEVERE] Saving turned off to prevent loss of data

Has anyone seen anything like this before?

I went to the first set of coordinates and chopped it out (it looked fine, just sand), and then replaced it with stone, but the error still appears when the plugin loads. What does Bukkit deem an invalid blocktype? Also, what does "Saving turned off" mean, since world saving still seems to work. And why does it say "Check world name for <username>". What does the world name have to do with it and how is it specific to a user?

Error does not appear when running vanilla or Bukkit with no plugins.

Here's some server info:

Code:

Linux moonbasesoftware.com 2.6.35-28-generic #49-Ubuntu SMP Tue Mar 1 14:39:03 UTC 2011 x86_64 GNU/Linux
java version "1.6.0_24"
Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)

CraftBukkit Build 740
Minecraft Server Version 1.5.02

Plugin list:

• SpawnX
• PickBoat
• CommandHelper
• SoupBowl
• Cookbook
• CraftBukkitUpToDate
• GlassPlugin
• LastSeen
• HomeX
• PlgDisableCmd
• FishPeople
• LyTreeHelper
• Residence
• AutoRepair
• Nethrar
• ChestLock
• HeroicDeath
• WorldBorder
• Simple Barter
• Snowballz
• ThisBiome
• Growbie
• DeathSign
• ThunderJoin
• SlowHealth
• AutoReplace
• PlugMan
• WelcomeMe
• OtherBlocks
• Parties
• HTTPConsole
• Bandages
• FireLord
• AutoPlant