-> Tap ALT key or press F10 to show the Menu Bar

-> go to Help Menu -> select Restart with Add-ons Disabled

Firefox will close then it will open up with just basic Firefox. Now do this:

-> go to View Menu -> Toolbars -> unselect All Unwanted/Incompatible Toolbars

-> go to Tools Menu -> Clear Recent History -> Time range to clear: select "EVERYTHING" -> click Details (small arrow) button -> place Checkmarks on Cookies, Cache -> click Clear Now

-> go to Tools Menu -> Options -> Content -> place Checkmarks on:

1) Block Pop-up windows 2) Load images automatically 3) Enable JavaScript

-> go to Tools Menu -> Options -> Security -> place Checkmarks on:

1) Warn me when sites try to install add-ons 2) Block reported attack sites 3) Block reported web forgeries

-> go to Tools Menu -> Options -> Advanced -> Network -> Offline Storage (Cache): click Clear Now button

-> Click OK on Options window

-> click the Favicon on SearchBar -> click Manage Search Engines -> select all Unwanted Search Engines and click Remove -> click OK

-> go to Tools Menu -> Add-ons -> Extensions section -> REMOVE All Unwanted/Suspicious/Incompatible Extensions (Add-ons)

-> go to Tools Menu -> Add-ons -> Appearance section -> REMOVE All Unwanted/Suspicious/Incompatible Themes (Persona)

-> Restart Firefox

You can enable your Known & Trustworthy Add-ons and Themes later. Check and tell if its working.

Try this: http://www.techishare.com/firefox/restore-default-address-bar-search-settings-in-firefox/

If that does not stick when you shut down and re-start Firefox, then you probably have something installed in Firefox or on your system that is changing the search engine.

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