Not sure if you ever came across this issue. I've got two trees under my umbraco tree, one being for the Polish content and the other - English. Hostnames and languages are definitely assigned correctly, and the site works as expected fetching correct language versions of eg. images, prompts from the dictionary and via user controls > dictionary.

However, whie queries in the searchbox direct to the correct result node id, they often display messages in the wrong language. It's a case of defaulting to English, rather than random switching of culture.

Any ideas what might help alleviate the problem?