Optimize your browser....ok. Defrag your Hard drive, Optimized. uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 57.0.4 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

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

jrmline said

Dell tech support "optimized" my browser creating a crazy bookmark problem.

Any idea what they did?

My bookmarks are still there, but no longer display in left bookmark sidebar and I can't access my existing bookmark folders to add new ones.

How do you know the bookmarks are still there -- where do you see them?

I'm not sure why, but some users seem to have problems with bookmarks related to hardware acceleration enabled, indicating some kind of incompatibility with their display driver software. You can try disabling hardware acceleration to see whether that makes any difference. This article will get you to that spot on the Options page: Firefox's performance settings.

You can check for problems with the places.sqlite database (bookmarks and history) in the Firefox profile folder.

• use "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page

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

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

jscher2000: How do I know my bookmarks are still there.

While they don't appear in the bookmark sidebar, they do appear if I click Alt then click on Bookmarks on the menu line that it adds to the top left of the browser.

Thank you for clarifying that.

So, hmm, what is wrong with the sidebar, then... Do the "three categories" show up there -- Bookmarks Toolbar, Bookmarks Menu, Other Bookmarks -- or not all three, or just blank space?

jscher 2000: No, the three categories are not there. Instead there are just three consecutive bookmarks from the first third of a bookmark folder that has more than 50. Weird.

Hopefully cor-el's suggestion will help: https://support.mozilla.org/questions/1198352#answer-1060329

I have tried the great suggestions provided above, but the problem persists. Other ideas? Thx!

If "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page can't repair the places.sqlite database then remove all places.sqlite files in the Firefox profile folder with Firefox closed to make Firefox rebuild the places.sqlite database from the most recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created
• http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

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

I do miss the extra repair features Places Maintenance included to be part of Verify integrity.

Thank you cor-el!! It took a couple of attempts, but deleting places.sqlite and allowing it to rebuild eventually solved the problem.