Okay, finally got the manual.
Your receiver will handle Dolby Digital, DTS, and Linear PCM over the HDMI inputs. So, if you are trying to listen to a lossless codec (such as Dolby TrueHD) from the PS3, you need to set the PS3 to output LPCM and not bitstream over HDMI. Your receiver can't decode (and thus, won't make sound) the bitstreamed lossless codecs.
Make sure that you are selecting the input on the receiver that corresponds to the HDMI input jack to which you connected the PS3 (e.g. "BD" is the input for the "BD IN" jack).
Don't connect the optical cable from the PS3 to the receiver. Only connect the HDMI cable for now. I don't know if the optical cable would override the HDMI input or not (I need to keep looking in the manual).