MVP audio Issue

[JUC]

Well, I have a possible problem with my MVP's audio. I know the forum is flooded with HD posts but if you can help please reply.

Basically, anything that is recorded or downloaded that is in dolby surround (i'm assuming its dolby), like TV shows for instance, has static/hissing coming out my speakers. Now--this is not that bad and only noticeable if you put your ear to the speaker and listen for it but it is there. Happens mostly on the front L+R, and real L+R. Now that i know about it it is really bothering me. The wife doesn't even notice it though. I have my MVP running by composite to my receiver which is doing the decoding and have tried different cables. Receiver is Yamaha HTR-5860.

Some weird things I have found when troubleshooting.
-The audio on any DVD stored on my server plays back fine. Even with dolby, or any other surround format i select. Audio is crystal clear.
-Recorded shows as well as downloaded shows exhibit the hissing/garbled noise.
-If I watch something in stereo the hissing goes away on the front L+R speakers.
-Noise is apparent on any of my selected decoders. Some are worse than others but always present.

So what is causing this? Since it happens on downloaded shows too ruling out my capture card. Since it works fine with DVD's stored on the server, I'm ruling out the MVP's output. Same with receiver? Maybe there is just something going on with the dolby soundtracks and the MVP? I'm totally at a loss. Any help would be appreciated.

Oh ya-could the optical out of the HD extender fix my problem?
Thanks
Juc