That's likely an issue with the Pinterest button that we're looking into. There's a few options that may fix things for you right now:
* Re-order the JFBCContent plugin to be the last plugin. This may let the youtube tag be parsed before our plugin tries to use it for the description when posting to Pinterest
* Re-order the JFBCSystem plugin to be the last plugin (but before any caching or optimization extensions), for similar reasons as above.
* Disable the Pinterest button in the JFBConnect -> Social configuration area. This will definitely fix things, but you'll be missing the Pinterest button.
I hope that helps get things going for you, but if you need anything else, just let me know.
Thanks,
Alex