I guess you didn't do a forum search before posting this ? There are dozens and dozens of posts about this. It's nothing to do with the Slingbox, your TV provider has implemented HDCP to stop you recording (or slinging) protected content. As the message says, remove any HDMI cable you have in your system and the problem will go away.
I have the pro hd and all of a sudden I am receiving a message on the screen and the slingbox will not work. Wondering if anyone has/had the same issue and how you fixed. I tried everything. The message is "the tv does not support this program's secure content. Replace the hdmi cable with component cables. Something to that effect, but it still won't work. Any help would be appreciated.