Try to rename/remove the secmode.db file in the Firefox profile folder.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Separate issue - your System Details show :
Installed Plug-ins : Shockwave Flash 15.0r.0 Shockwave Flash 16.0.r0 Shockwave Flash 19.0.r0 Shockwave Flash 25.0.r0
You should ony have Shockwave Flash 25.0.r0 installed. Having more than one version of a program may cause issues. You must remove the older programs.

http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html

Then reinstall the latest version.

Latest Flash Player Version: 25.0.0.171

https://get.adobe.com/flashplayer/ Direct link scans current system and browser.

Note: Other software is offered in the download.

https://get.adobe.com/flashplayer/otherversions/

Step 1: Select Operating System. Step 2: Select A Version (Firefox, Win IE . . . .) Note: Other software is offered in the download.

I hope you have backed up your passwords somewhere and are not relying exclusively on Firefox to store your passwords. Also I would suggest important passwords relating to maybe banking and email should not even be saved on Firefox.

Presumably Firefox works to let you sign in ok manually on sites where you remember your username and password.

Did you try to remove the secmode.db file like I suggested above?