Bukkit

What steps will reproduce the problem?
1.Installing Development version of plugin
2.Add items one after the other from and admin account in-game using the deposit sign.

What is the expected output? What do you see instead?
No NPE or error spam

What version of the product are you using?
Development version build unknown by me

Do you have an error log of what happened?
I sure do, Link Removed: http://www.mediafire.com/?7a23vpo5de65ud8

Please provide any additional information below.
The log near the bottom has errors, it shows that it cannot find "playername ID" But once the errors stop adding items to the shop using the in-game sign works for a while but then spams these errors.

What do you make of these Exote?