in version 1.8.3 if the key exists already when adding a key, it gives you a green info background that says the key already exists. It should be error (red) instead of info (green). 

ow_system_plugins/admin/controllers/languages.php

line 1135

OW.info('" . OW::getLanguage()->text('admin', 'msg_dublicate_key') . "');

need to be 

OW.error('" . OW::getLanguage()->text('admin', 'msg_dublicate_key') . "');

but since there is no OW.error then maybe this

OW::getFeedback()->error(OW::getLanguage()->text('admin', 'msg_dublicate_key'));

ps... by the way the proper spelling guys is duplicate not dublicate 

thanks ;)