Try updating to the most recent version of Firefox. Firefox 23.0 was released just today.

See:

• http://kb.mozillazine.org/Plugin-container_and_out-of-process_plugins

Thank you for helping me. I updated to 23.0 and today I have a problem with my default search engine Google being repeatedly replaced by Yahoo, despite my resetting it. Each time I try to carry out a search on Google, I get a blank page?

Can you access Google via the location bar?

• http://kb.mozillazine.org/Unable_to_search_or_add_new_engines

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check for problems with preferences.
Rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default value.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

To change the search engine in the location bar, you will need to do the following;

1. Select Toolbar Layout... from the Firefox Options
2. Drag the search item next to the location bar
3. Click ok
4. Choose the search engine on the search item, via drop-down logo list
5. Open Toolbar Layout... again
6. Drag the search item back to the customize window
7. Click ok

This is the only way to change the search engine. In older versions, changing the keyword.url value would change the search engine, but as of version 23 that no longer works.