Hello,

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Thank you!

Are you using the Firefox Sync service on those devices?

Yes, all machines (including my smartphones) are synced to the same account.

What in the way of extensions do you have installed on the desktop / laptop devices?

Are you synchronizing add-ons and preferences, in addition to bookmarks?

You can check for problems with the places.sqlite database file in the Firefox profile folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/

It is best to disconnect from Sync while performing maintenance/repair efforts to the places.sqlite database.

Yes, all of my browsers are fully synchronized, as they have been for quite some time. The issue started to appear only about a week or two ago, after my browsers automatically updated themselves to 35.0.1.

As for extensions, I'm only running Adblock Plus (on PCs and Android devices) and RealDownloader (on PCs only), both of which I've been using for a long time without issue.

As requested, here are a couple of screenshots from the same machine (ThinkPad T60), a few hours apart. In the first screenshot (BT1.jpeg), you can see the bookmarks on the bookmarks toolbar as I usually have them arranged. The second screenshot is a few hours later, and you can see that the bookmarks and separators have now rearranged themselves. If leave them alone and don't rearrange them back to the order I want, they will keep rearranging themselves until all of the separators are packed up to the far left of the toolbar, while the bookmarks will eventually be all over the place.

Just to let you fellas know, yesterday I've uninstalled Firefox 35.0.1 from all of my machines (including the Android mobile devices) and downloaded 34.0.5 from Mozilla's FTP site on one machine (the ThinkPad T60 I'm using right now,) and so far as I can tell, the problem hasn't shown itself yet. I'm going to wait it out another day or two and see what happens, then I'm probably going to install 34.0.5 on the other PCs and wait it out until the next update. Next, I'm going to reinstall Firefox on my Android devices and see whether or not it's there that the problem originates.