loss of audio on 46 CBS HD 58

[K9JAC]

I get my HDTV over the air and some programs on 46, CBS HD 58 have very low audio. Sounds like the only audio chanel is the sub-woofer. Its great when its the commercials and the audio returns for the program. But Cold Case is on now and the sub-woofer is the only audio. All the other channels are fine. Anyone else have this or is it my equiptment???  I have SPDIF on and the optic output to the receiver  All the other chanels work great. 58 does at times. Sig is 100%. It will change with out changing anything. Thanks

[waterhead]

This could be a problem with decoding the surround sound. I'm using the S/PDIF optic output from my PC to my surround system. If I don't select the S/PDIF output, all I get is the subwoofer.