What I understand from your post is that you're having problems with the video signal.
In this case, if you tried what's on the following links already, then I would recommend to change the Set Top Box resolution as a troubleshooting step only and even try to connect the Slingbox to a different Audio and Video source to discard the current one as a potential issue.
I've looked at all of those other forums and none of them seem relevant because I don't use HDMI at all, and I slingplayer isn't telling me I have a weak video signal.
I'll try changing the resolution output of my Tivo when I get home and I'll try a different source too.
Thanks for the reply.