I wish I could help, but I have the exact same problem. I bought a 55LM7600 a week ago and I can't get my ps3 to work with it either. When I try to change the resolution on the PS3 to 1080p i just get static and green lines all over the tv. 1080i somewhat works but I get the green static on the screen. The sound also keeps cutting out every 5 seconds or so. I picked up some component cables and those work fine, but I want to get HDMI working so I can watch 3d.
Just wanted to chime in and see if you ever found a solution.