I found something odd. I am working on a site that is purely english, no admin translation required. therefore I used settings.adminLanguages = [ "en" ]; in my config.cfc. This works nice as it should only display the admin in english and no dropdown for languages in the menu. however the system seemed to determine, either based on a cookie or on something else that i need german and switched to german. I can no longer switch back to english. I think while checking and applying the user language, the config setting is not evaluated.
I suspect this is based on browser header auto detection. It should be changed so that it will only assign an active language!
Fix for this has been applied and will be in the next snapshot release.