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

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

To see all History and Cookie settings, choose:

• Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history
• Deselect: [ ] "Always use private browsing mode"

Thanks Cor-El for your answer, but the mi FF allways remember history. So the issue still there.

You can check the session restore settings and prefs.

• http://kb.mozillazine.org/Session_Restore
• https://support.mozilla.org/kb/Session+Restore

Thank you cor-el but the issue still there.

I installed v12beta3, and the issue still there. So, I need to return to v11: instructions?

You can simply go into your Control program, and then Programs and Features, then uninstall Firefox Beta (don't remove any personal data). then go to getfirefox.com and download firefox 11!

Thanks Tylerdowner. So tell about the installed addons: they will be removed and I need to re-install them?

So long as when you uninstall Firefox beta you make sure that you don't instruct it to remove your personal data and customizations, you will be fine.

To make sure, Backing up your information can help you do a backup so it won't get damaged or accidentally deleted.

Thanks Tylerdowner, again and again and...!! All run perfect!