How can I change the address bar search in FireFox PERMANENTLY?

How can I change FF's address bar search permanently? It's stuck on mp3tubesearch. I tried changing it, but when firefox reloads, the search resets. :-/|||click a little grey arrow by search engines logo, "Manage search engine" then either "restore defaults" or just move the needed search engine to the top using the buttons provided|||Try clearing your browsing data or uninstall then reinstall the toolbar. Messing around in the options for a while usually clears things up.