I have a Sony DVP-CX995V DVD player connected to a Hitachi 42HDS52A TV. I used a HDMI cable about 15ft long to connect the two. If I lay the cable on the floor it works fine. When I tried to run it under the floor the TV won't communicate with the DVD!!! I ran the cable along the floor joists and thought that there might be some interference with other power and signal wires near it. So I just looped the wire from one hole in the floor to the other. Still no communication. It always works above the floor. I have a heating duct it goes near and the cable for the TV, and some 120v romex for the outlets.

The problem was with the cable. It was a 23ft. Atlona HDMI to HDMI connection. I bought a cable from a local store and it works fine. I am returning the bad one to Lenexpo Electronics, for a replacement. They were very good about it, and told me to try a new one, that they would send, before returning the bad one. If the replacement didn't work also, I could send both back.