For those that need to try to get this to work on Office 64-bit:
If the option to embed a video link from a web site is grayed out, open up Internet Explorer 64-bit and go to http://get.adobe.com/flashplayer/ to download and install the 64-bit version of Flash Player. Follow the instructions and run the application.
Once everything is installed, restart Office PowerPoint 64-bit and you should get the option to embed.
Now, for embed code, you need to make sure that the HTML code includes the EMBED tag and not the IFRAME tag. If it contains the IFRAME tag when you try to grab the code from YouTube, try this for a template:
<EMBED SRC="insert youtube link here" WIDTH="XX" HEIGHT="XX"></EMBED>
INCLUDE the quotation marks.
If it does not play during the slideshow, go to edit the PPT and try to Preview it by right-clicking on the video. If you get a Windows Media Player error, download 64-bit codecs from here:
http://www.free-codecs.com/k-lite\_codec\_pack\_64-bit\_download.htm
Then try again.
If not, I have no clue, because I still can't get my own videos to work. =)