Check your FF options.

From "Options" in "secrecy" tab, check If the setting "Clear FF history when FF close" is checked. IF it is checked, near there is options button for this... (for what exactly you want to clear when the FF close) check if you want FF clear the (ex.)"saved passwords" every time you close FF.

I suggest to set a "master password"... (to protect all your passwords)

Sorry for my english! (I have Greek version of FF)

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

It is possible that there is a problem with the files key3.db and signons.sqlite that store the encrypted names and passwords in Firefox.
Rename the files key3.db and signons.sqlite in the Firefox profile folder.
You can add .old to the file names (key3.db.old and signons.sqlite.old) or move them to another folder to make it possible to undo the action.
You need to set a new Master Password after renaming or deleting key3.db and all currently saved passwords are lost.
If that has worked then you can remove the renamed files that are no longer needed.

See:

• "Troubleshooting" in http://kb.mozillazine.org/Password_Manager

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

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder

thanks cor-el. editing the key3.db and signon.db files fixed the problem. I appreciate your help

You're welcome