My comment was made in the thread concerning the latest version of AFP. If it's the same thread, where are those posts? I made that comment about discussing it was because it was off topic.
In some blogs concerning this problem in Win 7, people found that disabling Flash solved their problem (I'm not going to chase those down again). The other possible fix was to make sure that "Enable alternative codecs for HTML5 media elements" is enabled in the Advanced Internet Options. It was enabled in IE 11 and, surprisingly, it's enabled in IE 9.
I rarely log into YouTube unless it asks me to. I can give that a try but it won't be until tomorrow night. I tried it in IE 9 but it wouldn't work for the video under question, as well as others chosen at random.