Somehow the translation of the blog templates doesn't work. I do have the files in blog/lang/*.php, and they contain the right references to the templates. But everybody sees the blog controls in English. Our CMS is still translated, so it doesn't seem to be a global problem.

Anybody knows what's going on?

Or is there some sort of override to always use nl_NL i18n? Basically all my traffic is Dutch anyways.

How I fixed it..

Part 1:
Old tutorials apparenly only wrote about enable(), set_default_lang() and using 'nl'. Full code for in mysite/_config.php

// Enable Translations
i18n::enable();
i18n::set_locale('nl_NL');
i18n::set_default_lang('nl_NL');

Part 2:
http://open.silverstripe.com/ticket/2102#comment:2
This also needs a lot of extra language files and strings for your widgets.

Part 3:
A patch that fixes included (<% include .. %>) templates source, so their i18n translation strings are sourced from the right namespace:
http://open.silverstripe.com/ticket/3400

Thanks Henk, I should have seen that before I patched all the templates concerned and added the "identifier>.ss." to the "_t(<i18n-name>, <string>)" calls.

Testing and including your patch as fast as possible in the released version is a must for SS if they care about the International - non English speaking country - users. Most normal users will not be able to fix this, or workaround, and then it is a showstopper.