I had the same problem tonight. Fiddling with the Audio settings of the cable box helped (making sure the digital out is set to DolbyDigital, not the non-descript "other" setting)
I find I need to crank the volume WAY up when using my receiver with the cable box just to be able to hear it clearly. All my connections are secure, so I think it's just a lousy cable box. (Pace 551).
I also notice that even though the guide says lost is in 5.1, my wonderful cable provider (Rogers Canada) seems to only provide it in 2.0.
Hopefully there is someone who can help us both out... Tonight's Lost was great, though.
