Really useful module, thanks!
When a box has been defined in a feature with an empty title you will see the following error:
Notice: Undefined variable: title in boxes_multilingual->render() (line 76 of /var/www/turner_ge/public/sites/all/modules/contrib/boxes_multilingual/plugins/boxes_multilingual.inc).
I've fixed this by making sure that $title is defined, the same as you do with $content. Patch attached.