Put on your glasses....?
I once had an idea, but then I lost it. So far no luck finding it again....sigh.
I don't play vids through the 8.1 tile interface. I play them from the 'normal' desktop, through a normal browser (Firefox). I'm also using Stardock software, specifically Start8. Don't know if that has anything to do with how things work on 8.1, though. I'm not having any issues with playing embedded vids. You do have the latest Flash software, don't you?
I think your best bet will be look behind the keyboard for the loose nut. Typically that's the root of most Windows issues.
Here's something similar with IE. Don't know if you are using that or not..
http://forums.adobe.com/message/5799534