I can understand the frustration with the issue you are having. In addition it can be a very easy fix. From what i have gathered, is seems you are running into the High Definition Copyright Protection (HDCP) issue that all the Cable/Satellite companies have on their Set Top Boxes. If there is any HDMI cable plugged into your Set Top Box, It will cause no Video. no Audio etc. The way we have found for Slingbox to work correctly, and still have full function of your regular at home Television is pretty easy. You will need Component Cables (red,blue,green,red,and white) coming OUT of the Set Top Box, and they will be going to the IN ports of the Slingbox. You will then need an additional set of Component cables. They will be plugged into the OUT ports on the Slingbox and lead to the IN ports of the Television. The Televisoin will need its source/input switched to Component if it is not already. You will not have to worry about your HD channels or programs because Component cables will still stream you HD channels without issues. Please remember to remove all HDMI cables from Set Top Box. I will provide some additional information below if you would like to take a look.
Hope this all helps!!
Sling Media Support
I think I am having a similar issue. I have the slingbox connected to the TV via HDMI. It is connected to the cable box using both HDMI and component (to avoid issues with High-bandwidth Digital Copy Protection). I am able to watch TV on the home television connected to the Slingbox OR on my mobile device, but not both at the same time. It is my understanding that you should be able to watch both simultaneously. Are you suggesting that I would have to replace the HDMI going from my Slingbox to my TV with component cables in order to be able to watch at home and on a mobile device at the same time? And if so, what is the point of even having an HDMI connection??