Plugin Help help with hungergames plugin!

So everytime i try to allow a non op to either do /hg join [thearenaname] it allows them to but says internal error it works with op but not non op people also they cant click the sign that allows them to join so im forced to make them do /hg join [TheArenaName] instead of just clicking the sign but i think the reason they cant click the sign is because of the thing that is occuring in the console as seen in the pastebin area but anyway just figured i ask for some help also here is the main link to it!
http://dev.bukkit.org/bukkit-plugins/thehungergames/
http://pastebin.com/nrCEDMQn