Symphony.

Do you have Nils’ lang_german installed?

You don’t need to install the German Language pack to get it working as the extension provides its own translations.

The extension enable-disable process must be a bit quirky.

There are some quirks related to extension handling:
http://symphony-cms.com/discuss/issues/view/372/

Markdown Guide updated to version 1.3 on 28th of September 2010

Added localization feature built by Nils Werner (phoque). Currently includes only a German translation dictionary file.

Sadly not compatible with Multilingual Field Extension