Hi Lars,
I don't think those things could be related. The search index may not work well with some languages, but it should still create the files in the index folder and you should see the indexbuilder statements in the log.
Are you sure you don't have the search index disabled by setting this to true?
<add key="DisableSearchIndex" value="false" />
Note that it is possible that you have settings duplicated in more than one place. It will use user.config settings for appSettings if the setting exists in user.config, and if the setting exists more than once the once closer to the bottom of the file wins.
Hope it helps,
Joe