If you restart FireFox and your toolbar has reverted back to its default settings and this happens every time you restart
FF try this before anything else.
First completely exit FireFox, then goto Start > All Programs > Mozzila FireFox, and click FireFox Safe Mode. You
will get a small box with a bunch of options. Select the option "reset toolbars and controlls". Then click "make
changes and restart"
This error apparently happens when a file called "Localstore.rdf" located in FireFoxes "profile folder"
becomes corrupt. Usually this happens because of a PC crash while FireFox is open.
I have not tried this, but also if you cannot access bookmarks or search engines as well as the toolbar pain, by deleting
the "Localstore.rdf" file contained in the folder "Profile Folder" and starting over will fix this problem
Uninstalling FF and reinstalling will NOT fix the issue, Been there tried that.
I hope this works for you....