video sites (except for the big ones) can be a bit tricky, because you need to bypass AV scanning for those. The default rules are very restricted and might not suit every environment.
Andre has written a very good article about streaming media and MWG 7 here: https://community.mcafee.com/thread/33699
Another topic that deals with video streaming for a certain site can be found here: https://community.mcafee.com/thread/32333
Those might help you when you create your rules concerning streaming and video bypass in MWG.
MWG 7.1.5 will make things a bit easier, as it has an improved streaming detection that allows to create better rules for this.