A suspicion of mine was confirmed today by a colleague in Narrowstep's New York office. His computer, on a leased line connection, started freezing. SO, he looked further. It turns out that the problem was the Joost application. As I has guessed, it turns out that the passive relay component of Joost's software SUCKS computer resource as well as bandwidth.
Previously, I stopped using Skype because it just froze my laptop and the same thing is happening again. And, of course, video is far more voracious and this problem is magnified for those where bandwidth provision is very asynchronous, especially at high downlink speeds.
This is also particularly galling if you're on metered charging, as most people in the UK are.
How nice of those funky guys at Joost to use us all to build their global broadcast network!