no usable connection to youtube live

please do not respond unless you know of what you speak!  This is a professional issue.

I do live remote encoding for webcasts across the world.  I use CDNs (AWS) and recently started to use youtube live (creative suite).

My office NEVER has difficulty connecting to CDNs (typically Wowza or the old Windows Media).  I cannot however maintain a viable connection to youtube.  Yet I CAN from other locations (all that I have tried)!

I have a 30/10 business connection with fixed IPs which shouldnt be a problem as the streams are usually 720 or lower (1.4Mbps).  Usually, the stream establishes for about 20 seconds, then starts buffering for about 60, then the pattern repeats.

it is NOT my gear, my network, my encode, etc....I can go off-site with no problems.  It must be something in the upload path to rtmp.youtube - either a protocol or port chock.  All my pings and tracert's look ok.

COMCAST - please advise.

Thank you