From MozillaZine Knowledge Base

Unable to search

The "XPL LinkScanner Firefox 2.6" extension can cause searches to fail [1] or Firefox may crash when using various search engines. Disable or uninstall the extension via "Tools -> Add-ons -> Extensions". For more information, see the "XPL LinkScanner" entry in the Problematic extensions article.

Search Bar not working and cannot add new search engines

Firefox 1.5: The problem is most likely a corrupt localstore.rdf file. See this article for a solution.

Firefox 2 and above: If the Search Bar no longer works and you can't add new search engines, the problem may be a corrupt "search.sqlite" file. [2]. Try the following solution:

1. Exit Firefox and go to your Firefox profile folder.
2. Delete (or rename) the file "search.sqlite".
3. Re-start Firefox to see if it solves your problem.

Related bug reports

• Bug 367473 – Navigation Toolbar's Manage Search Engine function did not work
• Bug 359564 – search.sqlite can be corrupted when running out of disk space, resulting in broken search functionality