Additional Detail Needed "Network Congestion..." Message

See screenshot below for error message.

During a webcast from a webcast vendor we see this message occur.

This is a webpage with an embedded windows media player that serves the audio.

At certain parts a flash video is played within the media player part of the window.

Occasionally for some users an error message will pop up inside the media player window when flash content is playing (screen shot below).

This causes the video and audio of the flash to stop until the window is refreshed via F5 or until the flash file ends at which point the presentation resumes with the next slide, poll question or whatever is next after the flash content.

The webcast vendor tells me that this error message is generated by flash but they do not have any documentation on exactly what triggers the error message.

Based on the message itself I have pulled our network monitoring logs from the WAN links at the offices with affected people, from our VPN routers, from The core routers at our data center, from the Firewalls, border controllers and from each router along the path to affected users.  None of the major routers were at more than 5% unitization (95% was available) and the lesser routers/switches were only at 15% utilization for the busiest of the lesser routers/switches.  Processor power on devices was similarly low being as high as 5% on routers and the firewall.

Additionally with VPN tunnelled users and remote office users being affected simultaneously, we are limited to about 10 devices that are in the common chain of devices.  These devices are configured to handle up to 10gigabits of traffic at any point in time and typically run at about 500megabits.  So there isn't a situation where this application is spiking.  The aaggregate bandwidth of these presentations during peak use is 175kilobits per second and the issue occurs with as few as 1 person doing a test.

Additionally with a test of 10 people we would see issues with 1 to 3 people at a time, not all 10.  For VPN Tunnel users and remote office users to experience the issue it would need to be one of the 10 common devices with the issue and if it was one of those devices with the issue it should manifest for everyone simultaneously, not individually and in small groups.

So I am looking for assistance on what is causing this since, despite the error message itslef, it is clearly not network congestion.

Is there documentation on what specifically trigers the message?  A low level doc with details would be most ideal.

Is there recommendations on what else to check?

Any suggestions on what to look for in the packets?