I have the exact same issue as you, Brian. I believe it's related to the 'chromeless' youtube player in some way. For those videos that don't work in mythnetvision, do they work when you navigate to them from <a href="http://youtube.com">youtube.com</a> in mythbrowser?<br>
<br>When I reverted this change so that they videos just played normally instead, I got working fullscreen playback again (and pop over ads. Hooray?).<br><a href="https://github.com/MythTV/mythtv/commit/e699820464d54c9ecebb5ec8621e70f2d985198e">https://github.com/MythTV/mythtv/commit/e699820464d54c9ecebb5ec8621e70f2d985198e</a><br>
<br>When it does work though, the chromeless player is far superior.<br><br>I'm currently using RC1 of Flashplayer 11.2 for AMD64. I think it's been like this across all versions of Flash I've tried.<br><br>-Alex<br>