<off topic rant>
What happens is that Google decides to show me the Google search engine in exactly the language I did not want, despite all my settings on all my accounts specifying one and only default language.
It will do so even if I explicitly type google.de, google.nl or google.fr. Whatever language I expect or want, I will get a different one.
This makes me suspect all requests to google.com are routed through a routine with the name "because_fuck_you()".
To add insult to injury, this does not just affect the UI language, but also the content, functionality and sometimes even navigation, and not always in the straightforward relationship between language and content you may expect.
And I'm not even one of those poor souls that lives in a multilingual country... </rant>