ive seen this happen before, there is something metal touching the back of your cd player, i know it sounds stupid but its true, i was putting a friends radio in his probe, everytime i set it down by the shifter and turned the car on. pop seen a spark i the back of the cdplayer the amp in it.. looks like a heatsink. and then we drive to walmart and got new fuses, was all good after i figured it out.