> which version from which source (tarball, distro-package..)
tarball Roundcube 1.3.3
>> In Firefox german is the preffered language
> the UI language don't matter - don't confuse langpack under addons for
> the browser UI with the preferred content language you can chosse in
> the settings between fonts and downloads
Could it has something to do with that accidently I logged in one
domain-interface to another domain/mailaccount?