I had the same exact problem. If I accidentally turned it off and then turned it back on right away, I would get this awful "digital" noise rather than sound. Turning it off on the back and waiting always cured it. I never did quite isolate exactly why the problem occurred except that every time it happenned, I had accidentally hit the remote and turned it off them immediately turned it back on.

I talked to Scott and he had me install the latest upgrade. this was about a month ago. At the time he said mine was the first he had heard of this but he did log it at the time.

He felt something was corrupted and installing the upgrade would do the trick. So far, no problems since the upgrade and reset.