We suddenly have one article that shows content from wrong language.

The pagetemplate is a simple article page that is used a lot. The site is translatet to three languages and it works fine overall. But suddenly one of the main articles is doing weird things. The page is translatet to norwegian (master language), swedish and danish. For some reason, the norwegian version suddenly shows the swedish version (swedish master-page, menu and all, not just the article content), both in view mode and in edit mode -> preview. If i go to edit I see the norwegian content in the fields. The swedish version and danish version shows correctly. I've tried editing and publishing both new and old versions of both norwegian and swedish, but nothing helps. What to do??

All other articles shows correctly.