Bukkit

What steps will reproduce the problem?
1. Have a vortex manipulator in the hand
2. type /vm [world_name] and press enter

What is the expected output? What do you see instead?
The player expected to be teleported randomly in the selected world. He is instead kicked out the server with the error message "Illegal Position".

What version of the product are you using?
1.2.1

Do you have an error log of what happened?
[19:23:24] [Server thread/INFO]: Player issued server command: /vm Ressource
[19:23:28] [Server thread/INFO]: Player lost connection: Illegal position
[19:23:28] [Server thread/INFO]: Player se d?connecte ... {english translation : Player is disconnecting}
[19:23:28] [Server thread/WARN]: handleDisconnection() called twice

Please provide any additional information below.
When the player try to connect again on the server, it kick the player again with the same error "Illegal position".

What are your current coords when you try the command?

There's no precise coords, the player just needs to type the command and then the bug appears. I already tried in several places and it always does the same bug, the player is kicked with the message "Illegal Position".

Any particular kind of world? i.e. overworld, nether, end

<<reply 2701419>>

It's generaly in an overworld world when this command is typed, but it does the same in any world, and in any world type
Edit : the bug seems to appear when we teleport from the Island Craft world to a vanilla overworld, into a non generated place. And an admin has suggested that the vortex manipulator teleports the player in some restricted coordinates, generating the message "Illegal Position"