If you have followed Marc's suggestions and checked the connectors for any shorts and you have done everything to verify you have a good power source (which I see that you have) then I would say it issafe to assume that you are dealing with a problem in the unit. At this point like I said before, if it is new unit take it back and get them to either service it; or if it is brand new get them to replace it. Don't waste any more of your time.

Now that aside, when you the level would blow the other speakers. How loud are you taking about here. I would ask Marc to help you here as I am not familiar enough with your unit as to the volume levels you can drive this at. But any unit if it is being driven hard or starts to heat up too much will go into protection mode. How long does it take for this to happen?