If it only happens during commercials while watching your local NBC station, then it's not the D* equipment. It's most likely an issue with your local broadcaster. It sounds as if all is normal through the network commercials, but the audio goes hinky when you hit the local commercials. Unfortunately, it's difficult to tell what's national and what's local, since some national sponsors buy local avails. During an NFL game, local promos come at the end of a cluster during a quarter. At the end of the cluster, the entire break is turned over to local affiliates.
If this never happens on, say, CNN or ESPN, then it's not your box.
Check with others in your local reception thread to see if there's a similar issue.
NOTE: Please keep topic titles specific. See my edit.
Walking the fine line between jaw-dropping and a plain ol' yawn.