nsTaggingService.js is a part of Firefox, although it's just as possible that it was fired up by an add-on seeking to modify your bookmarks as by you personally tagging or removing a tag from a bookmark.

Bookmark tags are stored in the same data file as bookmarks; it seems taht something has gotten crossed up in the database.

We had a similar post 2 days ago. Can you take a look at this one and see whether it helps in clearing out the unwanted extra bookmarks?

something added many bookmarks deleting crashes firefox

As for the original cause, I'm not sure. Hopefully not Xmarks, since that could affect a lot of people.

The forum software detected your Firefox as version 20.0.1. Is that correct?

Version 20 is not secure; Mozilla discloses security flaws after each new release. Is something holding you back from upgrading to Firefox 23? Please let us know so we can suggest solutions or workarounds.

If Help > About Firefox shows Firefox 23.0.1, you may need to clear the preference that is misreporting your version number. See: How to reset the default user agent on Firefox.

Thanks for your reply. I finally managed to get all those bookmarks cleared, had to let the machine run overnight. Since they Firefox went to a database (looks like it anyway) rather than a simple html file for bookmarks, it seems to have made things a lot more complicated. Since bookmarks were shared, each machine had the problem. On one machine I let it sit all night deleting, on the other I exported the bookmarks to html, edited that in notepad, then deleted all bookmarks and imported the html file, so both methods seem to work.

I'm stuck on 20.0.1 in this machine, am getting the "The update cannot be performed, please ensure there are no other Firefox instances ..." error. Tried all the fixes, no help.

On the other machine, Firefox simply freezes periodically. Trying to troubleshoot both of them. A total nuke and reload seems to be looming, but I don't want to have to rebuild two machines Again.

Thanks for your input!

Hi frnortner, when the updater complains, can you find firefox.exe in the Windows task manager (Ctrl+Shift+Esc) on the Processes tab? If so, you can select firefox.exe and click the End Process button to crash it and allow the updater to run.

If you find Firefox running hidden in the task manager after restarting Windows -- without starting it yourself -- this can indicate a malware infection. You may want to run some supplemental scans. These three tools are highly regarded (and free):

• Malwarebytes Anti-malware : http://www.malwarebytes.org/products/malwarebytes_free
• AdwCleaner : http://www.bleepingcomputer.com/download/adwcleaner/ (ignore banner ads for other products)
• SUPERAntiSpyware : http://www.superantispyware.com/

One note about your extensions: I think you should remove the "Updated Ad Blocker..." because AdBlock Plus is now more up-to-date and having both running at the same time might create conflicts.

Jeeze, I didn't realize I was running two adblockers! That's never good, two antivirus, etc. So I got a fresh cup of coffee, and went through everything installed and did some wel needed weeding. Used (retch) IE and downloaded the latest Firefox and installed it, after deleting the updates folders, and now with 23.0.1, looks like life is good again.

Good catch on the updates folder, I forgot about that problem. Glad to hear you're back in business.