Actually, that message that you found in the language file doesn't seem to be used in Geeklog. Which means that the message is coming from somewhere else.
A quick Google search indicates that it could be PHP complaining about the lack of a temp. directory, specifically for the "upload_tmp_dir" setting in php.ini. So this could be a problem with your local PHP setup. Check your php.ini and whether you've set a upload_tmp_dir.