Terry, Firefox is currently VERY flakey.
I posted on here last week that all my Bookmarks and toolbar buttons had vanished. Yesterday, my toolbar buttons vanished again between argos.co.uk and here. Fortunately I have Mozbackup, so I am able to restore settings and toolbar buttons are easy to get back.
My advice would be to download Mozbackup and make a backup of your passwords, bookmarks etc. immediately, because since the last Firefox update something isn't right.