What I'm getting from your post, is that you're getting no video from the Slingbox.
In this case, you can check the following links.
I'm providing those links, just because those are valid troubleshooting steps for you to try or for any customer with a video problem, is not something that will affect the Slingbox or anything like that.
If you tried those steps already, then you can do something like try a different Audio and Video source, set of cables etc, you can even try a different resolution from the Set Top Box.
Now, if after perform the troubleshooting steps, from our website, still the same problem, then you can contact the Sling Media Technical Support Department.
Once you contact the Technical Support, they can provide a final resolution, even one of the replacement options based on your Slingbox warranty if necessary.