Wordpress Multilingual Theme using Multisite

Question

I have a site that needs to be billingual, English and French. I've created two sites in WPMU, and set the language settings of the second to fr_FR. Under the directory:

/wp-content/languages/

I have fr_FR.po and fr_FR.mo files for the Wordpress backend translations, and it is working well. I've also created a theme called "oak" that is used by both the English and French site, with a folder called "languages". In the folder I have fr_FR.po and fr_FR.mo files with translations for all of the text in the theme (properly formatted).

The french site is not loading the translations from those files, and I'm not sure why.

All text on the site that needs to be translated is wrapped in

__('text', 'oak'); 

or

_e('text', 'oak');

Where 'oak' is the name of the theme folder.

The .po and .mo files are properly formatted, generated using poedit. Is there something I am missing to get the translations on the french site to work?