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

• https://support.mozilla.com/kb/Private+Browsing
• You enter Private Browsing mode if you select: Tools > Options > Privacy > History: Firefox will: "Never Remember History"
• To see all History and Cookie settings, choose: Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history
• Deselect: [ ] "Permanent Private Browsing mode"

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions 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.com/kb/Safe+Mode

Thanks, cor-el - issue fixed

You're welcome

Something enabled "Clear history when Firefox closes" in my Options settings (I didn't unless some odd key sequence can do it). If there is a plugin, malicious site, Norton SS (a prime suspect which also re-enabled its horrid toolbar), or a script then you guys might want to check into it and fix the issue. I lost dozens of username/passwords.

I would suspect Norton first as that software has done similar things before in the past by changing security settings without notifying you about that.