Try this.
http://www.pcworld.com/article/2048105/force-youtube-to-buffer-your-entire-video.html
I installed that about a week ago and set it up as they said. I am able to now force it to load even when paused. But the real problem is that youtube videos come from different places. One will download in no time while another will sit there and rot for hours. It looks like youtube has hit its wall.