i have a time warner cable box hookup to the rc360 via hdmi, and the rc360 is driving a sammy plasma, all works great and things; however, occasionally the rc360 can't detect the sound stream from the cable box and the screen displays "all ch stereo", whenever the sound works fine the screen would display "direct" meaning it is getting sound from hdmi.
here is something weird, when lack of sound occurs, if i would to unplug the hdmi from the tv the sound returns, obviously no video because nothing is driving the tv..
If the STB has optical out why not try that? You're not going to get lossless audio from your cable box anyway.
Cable and satellite boxes are notorious for screwing up the audio and video signal going to an AVR.