Let's see if we can't take care of this for you :)

First, you should update to Firefox 15.0.1. The version you are running is critically insecure, so you should update to the latest version ASAP. Update Firefox to the latest release

After doing that, try running https://addons.mozilla.org/en-US/firefox/addon/searchreset/

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

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

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

If there is a problem with searching via the default about:home page then try to reset the search engine used on the about:home page.

Reset the browser.startup.homepage_override.mstone pref via the right-click context menu to the default on the about:config page and close and restart Firefox to restore the about:home page to its default.

• http://kb.mozillazine.org/about:config

1. Open the about:config page via the location bar
2. Type in the Filter bar: mstone
3. Right-click the browser.startup.homepage_override.mstone line and select: Reset
4. Close and restart Firefox

If this didn't help then delete the delete the chromeappsstore.sqlite file in the Firefox Profile Folder and repeat the above.