There may be instances where certain media sources in your Library stop working. channel PEAR has absolutely no control over media sources - we do not host them and in most cases, we have no idea who does. We can't tell you exactly why a certain media source stopped working. You should take into account that the server hosting the media source may be experiencing an outage of some sort and may only temporarily be unavailable. It's recommended to not immediately delete sources from your Library that aren't working, as some do come back online.