In order to change your Firefox Configuration please do the following steps :

1. In the Location bar, type about:config and press Enter. The about:config "This might void your warranty!" warning page may appear.
2. Click I'll be careful, I promise! to continue to the about:config page.
3. services.sync.prefs.sync.browser.uiCustomization.state = true

Please post back with the results.

I saw that in the other thread about this issue as well, and did not try it, because it was reported not to work.

I had to create a new boolean - that entry isn't one of the defaults in about:config. I set it to 'true', and Sync started syncing. I waited until it finished, rebooted to my other copy of Windows, and uninstalled its copy of Firefox and deleted %APPDATA%/Mozilla/Firefox to get rid of my preferences and profiles.

I reinstalled Firefox, logged into Sync, and waited for it to sync. The UI is still the default, it's exactly the same as it was without that preference set. I even tried it all again, creating that preference before logging into Sync. The GUI was, again, not changed at all.

That value does not exist by default, and it does nothing, unfortunately. So, the report was correct. That tip is no good.

Well, this is weird. I logged back in to the first OS, the copy of Windows I first added that boolean to - and its layout has been changed to the defaults.

So maybe it did work, just the wrong way. I'll change the GUI back to the way I want it...again...and report back soon.

I can't even begin to imagine why this setting *isn't* a default, if it works...