Firefox Search Bar doesn't work at all?

[Yue]

Probably after I updated it to version 23 or 24, the search bar doesn't work anymore.
After I type in it, no matter I press "Enter", or click the search button on the bar, nothing happens. The bar still offers search suggestions, though.
Please help!

[Sam]

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

Go to Firefox > Help > Troubleshooting Information.
Click the "Reset Firefox" button.
Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
Firefox will open with all factory defaults applied.