I have tried once again to elicit the generation of a new and functioning "prefs.
js" file in the main page of my Thunderbird Profile, as suggested by Milo in his posting number 21 above. When I then close and reopen Thunderbird a new version of the file is dutifully created but I get the "Boing" of death and the following error message appears in a dialogue box:-
Windows Script Host
Script: C:\Documents and Settings\John\Application
Data\Thunderbird\Profiles\1iegx6og.default\prefs.
js
Line: 1
Char: 1
Error: Invalid character
Code: 800A03F6
Source: Microsoft JScript compilation error
Thunderbird then behaves as before, rejecting any changes I may make to the Junk Settings for each mail account and my incoming mail disappears as before as well.
It seems that the program is compromised and is even regenerating the file in a corrupted manner. I have uninstalled and then reinstalled a "new" Thunderbird from the Mozilla website and the newly generated replacement prefs.
js file was corrupt then too.
Does this error message give any new clue as to what is wrong and how to diagnose and fix the program, please?