I'm with Stealrhee - It's likely a primary power system problem, such as the alternator, battery, main UEC connections, ground, etc.
If I had to take a wild (unsustantiated) guess I'd bet you a nickel that you'll find a shorted rectifier in the alternator bridge. That will apply AC voltage to the system and none of the electronics are going to act normally in that case. It will also drain the battery quickly once the engine stops.
But that's just a guess. Perform a complete diagnosis before condemning/replacing anything.