* Corrupt extension files
   * Security software

  1.

     Open your profile folder:
         * (Firefox 3.5): See How do I find my profile?
         * (Firefox 3.6):
              1. At the top of the Firefox windowOn the menu bar, click on the Help menu and select Troubleshooting Information. The Troubleshooting Information tab will open.
              2. Under Application Basics, click on Open Containing FolderShow in Finder. A window with your profile filesfolder will open. 
        1. At the top of the Firefox windowOn the menu bar, click on the Help menuFirefox menu, go over to the Help menu (on Windows XP, click on the Help menu) and select Troubleshooting Information. The Troubleshooting Information tab will open.
        2. Under the Application Basics section, click on Open Containing FolderShow in Finder. A window with your profile filesfolder will open. 

  2. At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then click ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select QuitAt the top of the Firefox window, click on the File menu and select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.
  3. Delete the following files: 

   *
         o extensions.ini
         o extensions.cache
         o extensions.rdf 

  1. Restart Firefox. 

Firefox Help Search Welcome, playerjunglejosh. Dashboard | Sign Out Unexpected installation error -203 when installing add-ons This article is no longer maintained, so its content might be out of date. If you try to install an extension or theme, and receive the error message "Unexpected installation error -203", it is usually a result of extension configuration in your Firefox profile being corrupt or security software preventing those files from being updated. Table of Contents * Corrupt extension files * Security software Corrupt extension files Deleting these files will make Firefox recreate them (removing any corruption) the next time it starts. You will not lose your extensions or their settings by deleting these files: 1. Open your profile folder: * (Firefox 3.5): See How do I find my profile? * (Firefox 3.6): 1. At the top of the Firefox windowOn the menu bar, click on the Help menu and select Troubleshooting Information. The Troubleshooting Information tab will open. 2. Under Application Basics, click on Open Containing FolderShow in Finder. A window with your profile filesfolder will open. 1. At the top of the Firefox windowOn the menu bar, click on the Help menuFirefox menu, go over to the Help menu (on Windows XP, click on the Help menu) and select Troubleshooting Information. The Troubleshooting Information tab will open. 2. Under the Application Basics section, click on Open Containing FolderShow in Finder. A window with your profile filesfolder will open. 2. At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then click ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select QuitAt the top of the Firefox window, click on the File menu and select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit. 3. Delete the following files: * o extensions.ini o extensions.cache o extensions.rdf 1. Restart Firefox. This did work, but I had to do it like 5 times......