I love this plugin, and use it regularly. One thing I just came across is the following:
I am using WP Native Dashboard (allows you to change the language of the back end of a WordPress site for readability). Your plugin does not change from the installation's language when using this plugin.
I'm not sure if you are calling the WP_LANG constant directly, but perhaps
get_bloginfo( 'language' ) would fix this issue. Many other plugins work fine when using Native Dashboard, but your settings page remained in French when I chose English as the language within the plugin.
Just a heads up :)