Um, yeah, this is really annoying. It takes five minutes or less to actually start watching the video, if my laptop is running at the time.
There are a number of Add-Ons for Firefox that facilitate saving Youtube videos, like Video Downloadhelper. When I can’t just watch from the Youtube service on the Live Hub, I use that plug-in to save the video to my laptop, then transfer it to the LiveHub. Takes a little extra time and trouble, but it still ends up on my TV. 
