Some languages are not complete, maybe that is what causing your problem. Languages are located at the language folder. You can go in your browser to <your opengoo>/public/tools/checklang.php to see which language keys your locale is missing. You can start just by copying these missing keys to your language's dir.
If you want to translate those missing keys you can use the translate.php tool. To do this you first need to edit file 'public/tools/access.php' and add 'tanslate.php' to it. Then in your browser go to <your opengoo>/public/tools/translate.php