You could switch the audio options to bitstrea and let the receiver decode the audio, and that could be passed through the optical cable.
There may be an issue between the receiver and the TV, since the Blu-Ray works when directly connected to the TV. You might try a high speed cable if you're not already using one, but connecting to the TV with optical would be the recommended setup.
Set-up is Toshiba 1080p 37XV505 LCD TV, BD-C5500 Samsung Blu-ray player, and Samsung HW-C560S Home Theatre System. HDMI output (1080p) from C5500 to C560S, HDMI from C560S to TV.
I'm getting fairly frequent flickering with this set-up - I can avoid it by connecting directly from the Blu-ray to the TV via HDMI, with an optical audio to the receiver, but wouldn't I lose the HD audio capability (linear PCM) of the two Samsung devices due to the optical cable's limited bandwidth?
My cable box (1080i) works fine with HDMI through the receiver - no flickering at all - so is this a Samsung issue? Is it likely to be fixed by a firmware update (I have the latest on both devices)? I have disabled Anynet+ on both, disabled 24 fps, and I don't think it's an HDCP issue as even the menu flickers.