Hi Daz,

Try going to the Toolbars sub-menu (it's under "Customize" if you have the single-orange-Firefox-button menu, e.g. on Windows Vista, or under "View" if you're on Mac or the old-style Windows menubar) and unchecking "Add-on Bar" if it is checked.

If that still doesn't work, then maybe check what extensions you have installed. If you have an extension that wants to display something in your add-on bar, that extension could be forcing the bar to reappear after you have hidden it.

Hope that helps, --Jono Xia, Mozilla

You may have a problematic add-on that is causing the add-ons bar to re-open, for details of how to test this see https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes