Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All of them.

Start Firefox in Safe Mode {web Link} by holding down the <Shift (Mac Options) > key, and then starting Firefox. Is the problem still there?

Separate Issue; Your System Details shows;

Installed Plug-ins

Shockwave Flash 15.0 r0

Adobe Shockwave for Director Netscape plug-in, version 12.1 Adobe Shockwave for Director Netscape plug-in, version 12.0.4.144

Having more than one version of a program may cause issues.

Grab the uninstaller from here: Uninstall Flash Player | Windows Uninstall Flash Player | Mac Then reinstall the latest version.

Flash Player v16.0.0.235 https://www.adobe.com/products/flashplayer/distribution3.html Shockwave Director v12.1.5.155 http://get.adobe.com/shockwave/

Thank you! It was an old add-on that caused the problem. My passwords are back!

What one was it?

Hello,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.

FredMcD said

What one was it? Hello, I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily. Thank you for contacting Mozilla Support.

I can't remember the name anymore. It allowed Firefox to remember passwords from sites that didn't allow it. It wasn't compatible with my previous version of Firefox, but it didn't cause a problem before, so I never thought to remove it.

Thanks again!

The "Remember Password" extension that shows in the System Details list has been reported to cause issues with the passwords disappearing, so if you have this extension then remove (uninstall) it.

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