that is very odd
most dvd cd and radios are 12v dc, is this an original unit or a replacement?
truth be known the radios at home that plug into 120 outlets are really 12-24 v dc units as well.
do you have a wiring diagram for the unit or can you remove it from the cabinet and see its power requirements listed on the back panel.
does all your other 12 volt item work with the genny off?
sorry i wasnt much help
i did find a website with their prducts, maybe it can shed light on your situation.