[Plugin: Qtranslate] content are translate but wordpress not

Today, I started to stylize a new child theme from Twenty Eleven. First I could see all site translated when choose a language with flag selection. But without any explanation, wordpress stops to translate his own content, like “search”, “recent post”, “send”> I didn′t do anything about language. How can I go back with other language, I′ve already download mo files again and put in the same place, but don′t make any difference. Any suggestion?

Thanks a lot!