[piper6909]

Thanks Blue62 for all the suggestions. I went around and checked all the connections, including the grounds for a third time. Not hard to check, since there's no carpet. I also triple-checked the ignition switch, I forgot to mention in the original post that I attempted to change it while I was there. The replacement part was different, so I ended up putting the original one back. Still, no luck.

Then I remember years ago a mechanic told me that if you're having computer issues, disconnect the negative terminal, and tap it against the battery 3 times. I did that out of desperation, and for good measure I tapped my head and hopped on one leg 3 times! LOL I really didn't expect it to work, but IT DID!
Car fired right up! Windows work, locks and radio work too! WTF!??

I'm elated, but I still have an uneasy feeling that whatever the real issue is will end up biting me in the arse, at the worst possible time.

And for the heck of it I just plugged in the Durametric and it communicated with both alarm modules and the airbag module. No problems found on any of them!