I am having the same trouble since yesterday. None of the ports are working. What do you think it could be? Have you had any luck yet? Please let me know and i will let you know if i figure something out.
I have a LN40B550 TV. Suddenly today none of the HDMI input ports are working. I have tried connecting them to the output ports of a Roku streaming video player and two laptops that send HDMI output fine to other displays. The Roku also worked fine when I connected it via the composite video port. When they're connected on HDMI, I consistently get an error message: "The source is not connected. Please check connection again." Is there something in the settings that I could try, to fix this?