Used to work fine. Now it fails and says "are you sure the native client is installed ?" Duh, yeah !
The native client passes the connection test. All the paths are correct. And like I said, it used to work (yesterday). I even tried removing it and re-adding it. No dice. Maybe Youtube changed something ?

Looking at the browser console, it says:-

null ExtensionCommon.jsm:740

Unchecked lastError value: Error: An unexpected error occurred ffmpeg.js:14