Turns out the the plugin is not necessary anymore (as of Woocommerce 2.2)
All you need do is use the internal translation, which for some reason doesn't automatically show after upgrade (it should).
To get this done:
1. check that your config.php sets dutch as default language, using the line
define ('WPLANG', 'nl_NL');
2. In Wordpress, go to Woocommerce > System status > Tools and click "Force Translation Upgrade"
3. Done. That is, it worked for me.
You can find this at: http://docs.woothemes.com/document/woocommerce-localization/