Not sure about your model but my Kenwood DNX7200 completely tripped out when I fast charged the battery one day. I took it in to the local ICE shop and they had the whole thing out, no fuses blown, so they just reset it somehow (not sure but I think they said they just left it on the bench for about 1 hr!) and re-fitted it. All the presets were lost but it was working fine.
They did suggest that maybe it had freaked out if the fast charger surged the power too much and that I should put the side lights on if I ever disconnect the battery or anything so the lights take the surge and not the (more expensive) stereo.
I haven't tried that yet but has anyone else?