Sudden Problem

So my PDX-5, DQXS, Alpine SPX-Pro and Pioneer Premier and stock BMW 5 Series HU setup today is playing beautifully on my trip from DC to Richmond. I stop for gas. I crank it up afterward and I hear LOUD, irregular thumping sounds from all the speakers and no music. I pull power on the DQXS, but thumping continues with no music. Only way I'm able to stop it is pulling fuse on the PDX-5. Anyone have any ideas what is going on? Thanks in advance.