Well I am pretty new to Yii and I’am not quite sure, if it is a bug or maybe an intension. While configuring internationalization, i discovered, that Yii does not support the translation of internal messages of classes like CGridView for composite locales like “en_gb” or “de_de”. So if you set such locales for, let’s say, proper date formatting, you can face a situation, where everything is translated, but the zii and yii messages are still in english and since everything else is working, it’s not very obvious, what’s the reason for such behavior.
The reason is the absence of correspondent translation folders in /framework/messages. So you can get it working by copying the content of the folder with the translations for your target language in /framework/messages (for example "de") into newly created folder named after your locale (in my case "de_de") at the same place.