My pm4001 goes mute after a minute or so of playing, a little red mute light comes on and the amp basically freezes, can't change the input selector or un-mute with the remote, have to switch off and on again. The little playback I do get has an odd fluctuating sound quality, no consistency of tone or anything. This is a well-kept 2nd hand amp (ebay, sorry!) which I have just set up for the first time, I am really disappointed as I have gone hungry for weeks to pay for a new system. The only thing I have found on t'internet is that it might be a blown fuse, any help at all will be greatly appreciated, thanks -KJ