"David E. Ross" wrote

| The failure was NOT a case of a Thunderbird process still running. As
| my original post in this thread indicated, I got an error popup that
| said I needed at least Windows 7 to install the Thunderbird update.
| However, I do indeed have Windows 7.

You probably know this, but you might try
running Process Monitor to see what it does before
it quits. That might give you a clue as to where
it's getting its info.