Not sure if you have solved this problem or not, but we've been fighting it for the past few days. I believe we have found a solution.
We have a couple of NSA 2400s using failover. To solve the problem, we logged into the firewall, expanded Security Services, clicked on Gateway Anti-Virus, clicked on Configure Gateway AV Settings, then checked "Enable HTTP Byte-Range requests with Gateway
AV".
Hope this helps.
To RDM_833:
Sad to say, but it really has taken me this long to circle back to this, make the change and actually test it.
Your Solution: "Enable HTTP Byte-Range requests with Gateway AV" on the SonicWall devices, DID IN FACT FIX THE PROBLEM. Bravo! Not sure how you found this, or made the correlation...whatever the firewall is doing
or not doing, the byte range request issue was breaking the streaming connection.
Thanks again, hopefully this will help other people who have this issue. There is almost no error logging or any thing else to help identify this issue, which makes it all the more frustrating.