If this was mine I'd start with the reset noted at page 24 of the link to follow.
HOWEVER some folk didn't set up their HT so they may not be able to set it up and you must be a little comfortable of the initial setup.
Link -> http://store.sony.com/wcsstore/SonyStyleStorefrontAssetStore/pdf/warranty/SEL-asset-208847.pdf
I own a Sony HT-SF470 Home Theatre system. This past weekend, my dog had a nap on the remote control for it. Everything worked perfectly up until that point. When we tried watching the hockey game that night, all we could hear was the crowd in the stands, and the action on the ice. There seemed to be no commentary at all. We turned the receiver off, and listened to the game thru the tv speakers. There are some channels (CBC in particular) that sound absolutely horrible. The only way we get any kind of intelligible sound is by setting the sound field to Movie D.C.S. If we set it to Sports, it's really echoey. Any other field only has sound coming out of the sub woofer. BUT... some commercials sound normal on that channel. Conversely, there are some channels that sound normal but the odd commercial is missing some of its sound, or it's coming out of the sub woofer. I have reset the system back to factory default, and it hasn't fixed anything. I tried contacting Sony via live chat and I didn't get any resolution there. (I'm not convinced they actually know anything). I also have a PS3 hooked up, and Netflix sounds muffled as do any Blurays I play. As I have already stated, the only thing that has happened is a fat dog sleeping on the remote. Prior to this, everything worked perfectly. Any help anyone could offer up would be greatly appreciated.