Try to restore the key3.db and signons.sqlite files via the Time Machine in case the current files are corrupted.
If this isn't possible then remove the current key3.db and signons.sqlite files to make Firefox create new files.

See Troubleshooting:

• http://kb.mozillazine.org/Password_Manager

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder

Without doing anything, all passwords reappeared one day ! So now I wonder what bevaviour is this ? can I recover passwords stored in FireFox from Time Machine ?

The only way to merge passwords is to export existing passwords via this extension and swap the two files key3.db and signons.sqlite to get the other set and then re-import the saved passwords.

• Password Exporter: https://addons.mozilla.org/firefox/addon/password-exporter/

FF does not automatically fill in my logins WHy not ?

Make sure that you do not run Firefox in (permanent) Private Browsing mode.

• https://support.mozilla.org/kb/Private+Browsing

• Tools > Options > Privacy: Use custom settings for history
• Deselect: [ ] "Always use private browsing mode"

You can also check the value of the signon.autofillForms pref on the about:config page.

• http://kb.mozillazine.org/signon.autofillForms

Remember I am a Mac user. The Use Custom Settings for History is under Preferences (not Tools) This setting is not saved. It always is Remember History

Sorry about the menu path for Windows.

Seeing "Remember History" means that all history and cookie settings are set to the defaults.
The "Use custom settings for history" selection allows to see the current history and cookie settings, but selecting this doesn't make any changes to history and cookie settings.

If the settings are correct then you may have an extension that is preventing filling passwords.

Do all the names and passwords show in the password manager?

Do you get a drop down list when you type the first letters of a stored name in a website form?

It seems to work now, but who knows for how long ? there are always surprizes...