Was this in conjunction with YouTube for Schools?
I had some customers having issues with it and it was an issue with playing videos with the flash player in IE and FF. Navigating to YouTube and selecting the option to use html5 resolved it in the interim while we waited for Google to fix the issue (It was a problem on their end), and it seems to be fixed as of around mid last week.
Also if you are blocking googlevideo.com that could be an issue, Google seems to be using that as a CDN for YouTube now.
Was this in conjunction with YouTube for Schools? I had some customers having issues with it and it was an issue with playing videos with the flash player in IE and FF. Navigating to YouTube and selecting the option to use html5 resolved it in the interim while we waited for Google to fix the issue (It was a problem on their end), and it seems to be fixed as of around mid last week. Also if you are blocking googlevideo.com that could be an issue, Google seems to be using that as a CDN for YouTube now.