Default language not visible in WPMU "Site Wide Settings"

I'm trying to set the language to dutch in a new install.
I've added define '('WPLANG', 'nl_NL');' to wp-config.php, added the language files in the buddypress/bp-languages folder.
And now I have to set the language in the Side Wide Settings.
But the dropdown menu isn't visible. In fact.. it isn't showing anything.
Any ideas what I might have missed?