I feel silly responding to myself, but I went on testing with the
replacement PIC and figured out what had happened (by accidentally doing
the same thing to the new one).

I had started programming it when I realized I had made a mistake in my
code, so I hit ^c to interrupt the programming.  Apparently this left
the poor little PIC confused.

I tried programming it with the factory-loaded contents I had saved
before, and this time told the software to overwrite OSCCAL and BG.  Lo
and behold, not only is the second one fixed, but the original "broken"
one was fixed by doing the same thing with its factory-loaded contents.

I'm feeling so much relief right now that it completely hides my
embarrassment :).


Rick Luddy wrote:
> Things were working fine for about an hour of testing when at some point
> the PIC died.  I tried programming it with a known-working program,
> still broken.  I replaced it with an identical PIC and programmed that
> with the same program and it worked.

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