I am almost ready to release v2 of the easy youtube player but out of a sudden everything stopped working. I thought at first my own developer key got banned for incessant re-loading locally, but even Google’s own example is broken.

The solution to it seems to be to change the URL of the embed code:

// broken
      swfobject.embedSWF('http://gdata.youtube.com/apiplayer?key= ... ')
// working
      swfobject.embedSWF('http://gdata.youtube.com/apiplayer/cl.swf?key= ... ')

Thanks do d.kunchev who pointed this out on the mailing list