Hi, hold down the Shift key when you start Firefox to start in Safe Mode. More - Diagnose Firefox issues using Troubleshoot Mode.

If it works in Safe Mode, disable any theme or add-ons you have - 3-bar menu > Add-ons > Themes/Extensions and restart Firefox; then if it's OK, re-enable them one by one until you find the culprit. You may need to restart Firefox after enabling some add-ons.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you!

Still unable to see any of my bookmarks even in Safe Mode. Thanks for your suggestion.

Even after refreshing Firefox, I still get a red banner at the top of my screen saying, "The bookmarks and history will not be functional because one of Firefox's files is in use by another application. Some security software can cause this problem." I have tried the 6 or so suggestions after selecting the "Learn More" button on the banner. I even turned off my security software and re started Firefox to see if that was the problem. Still got the banner.

Kill Task in Task Manager

Please use more than 1 scanner as each uses diff tech :

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Save your Report and google each before deleting anything as do not want to delete something you need, If need help :

• https://forums.malwarebytes.com/topic/9573-im-infected-what-do-i-do-now/

Post in only 1 forum, then wait.

Please let us know if this solved your issue or if need further assistance.

Do you mean either of these errors?

• https://support.mozilla.org/en-US/kb/The+bookmarks+and+history+system+will+not+be+functional
• http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

Both these are about problems with the places.sqlite database file. The former means that other software is using this database and that Firefox can't open this file for writing. The latter means that places.sqlite is corrupted and needs to be repaired or a new file needs to be created (i.e. you need to remove the current places.sqlite files).

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

See also:

• http://kb.mozillazine.org/Locked_or_damaged_places.sqlite
• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file