it seems that this CS version does not use the HTTP “Accept-Language” header to select the language which will be displayed. My browser sends “en-us,en;q=0.8,de-de;q=0.5,de;q=0.3” and CS does display the pages in German. After login everything is fine, likely because of the selected Locale in Your Stuff, Preferences.
Maybe CS is using the IP and a GeoDB to identify the source country but this is not what I expect.
Anyone to confirm this?