Try connecting it with a different cable, such as a yellow AV cable.
What's probably happening is that the game console is sending a 480 resolution, which may not be supported through the HDMI port. So first, you want to change the output resolution from the game console to 720p or higher, and you can do that by attaching it with a connection we are already know works, such as the AV cable. Then, once you see the screen, you can change your video output settings by accessing the game consoles menu system, under the video settings.
Once you've done that, you should be able to attach the HDMI cable and change the television to the HDMI input associated with the game console and see the PS3 menu.
Does that help?
Have LE40R784D and just tried to use Playstation 3 with this tv - getting 'No Signal' message when plugging into the HDMI port, this is the first time we have sed the HDMI port - any suggestions as to what could be the problem? Thanks