When I first bought my car, I had an old Kenwood headunit (well, like 3 years old)...
I installed my system, everythings goin good for a couple months. Next thing you know my car starts dying. I drove around w/o my faceplate on to *charge the battery*, and realized in an hour or so that when the radio was off, the amps still stayed on.
I replaced my headunit, and problem solved. It happens I guess lol.