Thanks for all responses received thus far.

I installed a known good battery, and when I turn the key, nothing happens (i.e., no sound from the solenoid, no cranking, no dash lights, NOTHING!).

I then re-checked the fuses in the engine compartment, and found that fuse 1 (a 15 amp fuse) was blown. I replaced the fuse and put the key into ignition without turning it. The LED odometer lit-up, as well as the LED clock. Also, the key-in-ignition warning chime started sounding. As soon as I turned the key to try starting it, again, NOTHING!!! I then then rechecked the fuses, and again, fuse 1 was blown.

There is definitely one (or more) shorts somewhere.

I'd like to try disconnecting all the computers, and then insert a new fuse and turn the key. If the fuse does not blow, then I will try reconnecting the computers one by one to see if one (or more) of them are causing the fuse to blow.

I can't do this now, as the car is with the owner, and I need his permission.

Maybe I should run away from this car, but I was told the car ran beautifully before the unfortunate owner hooked up the battery wrong.

I may also just offer him scrap value for the car ... maybe he'll take it. I already located a donor car that was wrecked. Maybe I'll end up with a really good car.

Will update you all as things progress.

Alex