Welcome to the Slingbox answer forums. I have a few questions about your setup. Is there any HDMI cables in the mix at all. This very well could be some sort of new copy right protection. I will post a little more on those protections below.
When I connect my set-top box to my TV with HDMI connections, I can't stream video at all using any version of SlingPlayer. Why?
If these do not help what I would suggest doing is running the componet cables to the TV and see if you get the same issue. If this issue persist to the TV than you would want to contact your cable provider to get this issue fixed.
Sling Moderation Team