Are you referring to the primary password? If so, here is how to reset it: Go to tools>Developertools>error console - enter this text

   openDialog("chrome://pippki/content/resetpassword.xhtml")  

- the Reset button should appear. All passwords for accounts will be deleted

Thank you for your very prompt reply David.

I have followed your advice and now have the password vault available again. I had already changed all email passwords via webmail so will input the email addresses into T'bird in a day or two.

Thanks again,

Caison.

You're very welcome .

Hi again David Unfortunately I rejoiced too soon! When I was entering the first email account again, after clicking Done TB said it had noticed my account was linked to a calendar and an address book called Will's address book and Will's calendar. I don't know a Will and don't use a calendar. Is this part of the intrusion that locked me out of the primary password input? I think I would feel happier if I knew these files that remain after deletion of TB were deleted as well, then a reinstall would be uncontaminated and I wouldn't have to worry about something coming back to bite me at a later date. I'm grateful for any help, many thanks Caison