[Plugin: The Events Calendar] Translation

I have set the language to
define (‘WPLANG’, ‘de_DE’);
in the wp-config
and in the /plugins/the-events-calendar/lang
have
the-events-calendar-de_DE.po
the-events-calendar-de_DE.mo
but still the site is showing english texts on the homepage
i am working with buddypress
http://www.meine-orchideen.de/events/zweiter-test/

http://wordpress.org/extend/plugins/the-events-calendar/