"An internal error occurred while attempting to perform this command"

The title keeps showing up... i have installed commandbook and world edit for my server... but this keeps showing up! HELP!!!!!!!!!

it says:

14:22:08 [SEVERE] Error occurred while enabling WorldEdit v4.7 (Is it up to date?): java.lang.String.isEmpty()Z
java.lang.NoSuchMethodError: java.lang.String.isEmpty()Z
at com.sk89q.worldedit.bukkit.BukkitConfiguration.load(BukkitConfiguration.java:89)


commandbook has no record of saying there is an error..... HELP.

 

you need to post the server log.

oh, and btw: did you read the big red thingy on the top?

 

post the server log? how do i do that????? and i will

what did i do wrong?
and ps i dont understand thingy in rred xD

EDIT by Moderator: merged posts, please use the edit button instead of double posting.