Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

I followed the process, but it didn't work.

You're welcome

I am having this problem as well. What is the fix?

What I ended up doing was re-installing the whole Firefox and that seemed to work. No problems yet, also save your favorite's link onto an e-mail draft. Unfortunately, I didn't do that.

I had the same problem. Even after reinstalling and updating everything. It still disappeared, so I figured just live with it. I was getting sick of those search ads that follow you. So I installed Adblock https://addons.mozilla.org/en-us/firefox/addon/adblock-plus/ The problems gone now.