I am new to the world of home theater and especially the use of hd projectors. I just received my optoma hd 20 projector a couple of days ago and I am having problems trying to connect it to my Comcast cable box( Motorola dcx 3400 with 25' hdmi cable). Whenever I connect the cable whether directly to the projector or through my receiver the image will appear for 5 seconds and then everything goes black. A faint white light is still coming out of the projector lens but nothing on the screen. If I manual switch inputs and go back the same thing happens. I have tried multiple cables and none seem to work. the blueray works fine. And I can get audio to the reciever from the cable box. Anyone have any ideas on how to remedy this?