Misterious electrical problem

I have a 1993 Audi 90CS. It has an electrical problem, that no one seems to be able to find the cure. With the hood completely closed, the car starts, the hazard lights work. Nothing else works, no windows, no radio, no lights. If the hood is unlatched, everything works.

The question is why does unlatching the hood cause everyting to work? How do we fix the problem so the hood can stay latched.

Look for a faulty ground connection.