Having the exact, same issues. I have two HD-PRO devices. One is connected to the Internet through a 100mbps connection at my office. When I try to view this box from the outside world, the connection shows about 500kbps and the picture is terrible. On my office network, I get 8mbps and a terrific picture.
When the computer is connected to the same router local area network as the SB, there is no involvement in the stream transfer with the outside internet, so speeds are determined by the cat cables, the router itself, and the electronics of the SB and the computer. In my network, I typically get 8000 kbps streaming speeds under such a connection. When the computer is not in the same LAN as the SB, then the streaming goes through at least two routers (the one with the SB on it and the one with the computer on it) and two modems, plus all of the other switches and connections in Internet land between the two modems. Fastest speeds that I experience then have been 2000 kbps, but often are much slower -- down to as low as 300 kbps -- and sometimes even less for a few seconds, to the point that the streaming may stutter or stall for up to several seconds. If you have the "video quality" set to "Auto" (which I believe is the default setting) on the bottom of the streaming window when you are viewing the SB stream with a web browser, then I believe the quality will adjust itself periodically to match the streaming speed. But if you manually set it to a particular quality (such as "best" or "best/HD", then you might trigger stalling or stuttering if the transmission speed drops.
The only thing that I have been able to do so far to optimize my streaming is to apply free internet transmission optimization software to my computers, such as TCPoptimizer.exe. I've also seen some other folks on this forum note that users with DSL modems can further optimize their transmissions by adjusting the MTU setting on their router.
So I'm seeing the same behaviour.
For the past year or two I've had no problems, however when I connect through my home network now, I'm getting speeds of 40 kbps (Blank screen)
If I drop the qualitly from HD to BEST however, the bandwith suddently picks up to around 8000 kbps and everything works.
Switching back to HD mode, and the bandwidth instantly drops again down to 40 kbps and you lose audio and video.
Rebooting Router/Switch etc has no effect.
Connecting via my Smartphone/Tablet works fine without any issues both within my network (Via Wifi) and outside (Via 3G)
Could this be a hardware problem?