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

Some web sites stop the Password Manager from working. A work around is; Go to the Mozilla Add-ons Web Page {web link} (There’s a lot of good stuff here) and search for a form-filler.

Make sure that you do not run Firefox in permanent Private Browsing mode (Never remember history).

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

• Tools > Options > Privacy > Firefox will: "Use custom settings for history"
• Deselect: [ ] "Always use Private Browsing mode"

Details like websites remembering you (log you in automatically) are stored in a cookie.

• Create a cookie 'allow' exception to keep such cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Tools > Options > Privacy > "Use custom settings for history" > Cookies: Exceptions