WIth 0.8.6d i also dont have this plugin. But if you download for example some nightly build, you will have it. I downloaded archive, not installer. Extract it somewhere and there you go, new awesome mozilla folder ;P
Hey. I don't know if that will fix your problem. On my PC i had pixelized video in VLC, not in other players. So i simply changed image(? i'm not using English version) output to DirectX, restarted the player and now it works ok.