I have the same problem with my Mums 1080p Samsung TV.
Using a HDMI cable I can plug in my laptop and it works fine, I plug in her DVD player using the same HDMI cable and I get nothing, plug in my PS3 using the same cable I get nothing. Take PS3 home to my house with 720p TV using the same HDMI cable and it works.
no farking idea why and it drove me crazy trying to figure it out.