I think there might be a fusable link somewhere near the battery on one of the main leads. I had the same thing happen to me a while back, it turned out to be an old broken wire inside the rubber casing of the ground (the actual metal strands had pulled apart inside the insulation). I ran a new ground and everything went well.
You might check the main fuse and others to make sure everything is ok.
If it isn't a fuse, get a volt-meter and test the continuity from the negative terminal hookup to a ground on the car. Test the positive feed as well. Start from the power source and start working your way out.