My slingbox Pro-HD works great until I try to watch my TV and put my Iphone app on. I can watch my cable on my Iphone fine until I trun on my reciver and my home TV. Then it will tell me no video found and it just play's the sound on the Iphone. Why does this happen ? My TV is hooked up from the cable box HDMI to HDMI on reciver then HDMI to the TV.