I'm having problems with my Onkyo rc270 communicating with my 5600... I posted this on the LCD forum as well...
I posted on the official 55LW5600 thread, but did not get a response. I have ARC setup on both the Onkyo and the TV, however the only audio that gets passed through is 2 channel audio. I have the PS3, Boxee Box, and Tivo connected directly connected to the TV, and the 270 connected on HDMI 1. Receiver is on TV/CD and TV has Simplink tuned to the HT Speaker.
I also have a Xbox 360 connected directly to the Onkyo and the audio plays correctly (dolby digital or other).
I've tried doing a reset on the Onkyo and made sure the firmware was up to date on the panel and the receiver, nothing has worked so far. I have the Amazon branded hdmi cables attached, and they are 1.4 spec.
Any suggestions would be appreciated. If there is no solution, maybe someone could offer a workaround?