rest of the story..."

It turns out the problem was the alternator. I did a number of things that were recommended in my original thread, and the car would work normally for a day or so and then the warning light would come back on. About a week or so later, while my wife was driving my daughter home from school, the engine failed. The way that it happened told me that it was clearly the alternator. I had never seen any of the other earlier problems associated with an alternator failure, which is why I didn't suspect it.

Anyway, I replaced the alternator and now the car runs as good or better than it ever has.