In my custom I18n component I do this:
Yii::app()->cache->keyPrefix = Yii::app()->getId() . $this->activeLanguage;
Yii::app()->urlmanager->cacheID = 'cache';
Yii::app()->urlmanager->rules = include("{$this->urlRulesPath}/{$this->activeLanguage}.php");
Yii::app()->urlmanager->init();
Yii::app()->cache->keyPrefix = Yii::app()->getId();
In the first line you can see I change the keyPrefix of the cache-component so it’s possible for the urlManager to cache rules for each language. When YII_DEBUG is enabled I get an error because CDummyCache (which is set in debug-mode) doesn’t have the property keyPrefix. I suggest to extend CDummyCache from CCache.