Denon AVR-689 Problem with Crackle

Got a new Denon 689 and after playing for a while, either with the tuner or tv the speakers begin to crackle and pop and then the cound cuts out. Happens on both surround and stero modes. Tried hooking one speaker up at a time but same thing happens. Do you think it is defective?

Or could there be a short somewhere causing it?

Thanks