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Unable to start Firefox.

New User

Unable to start Firefox.

Whilst viewing Youtube Shockwave Flash sent an error message to say it had crashed. I closed Youtube and reinstalled Flash from Adobe and continued to download a website to convert Youtube music to MP3. That was unsuccessful so I uninstalled the website and I had to restart my computer, but in doing so Firefox refused to open at all. so uninstalled it and reinstalled it but it still refuses to open. I looked at properties and an error message indicated that incompatibility was detected but am not sure with which software. Can you assist please. Thanks Diane Walsh

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SUMO Contributor

Re: Unable to start Firefox.

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

  1. Download the latest Desktop version of Firefox from and save the setup file to your computer.
  2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
  3. Delete the Firefox installation folder, which is located in one of these locations, by default:
    • Windows:
      • C:\Program Files\Mozilla Firefox
      • C:\Program Files (x86)\Mozilla Firefox
    • Mac: Delete Firefox from the Applications folder.
    • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
  4. Now, go ahead and reinstall Firefox:
    1. Double-click the downloaded installation file and go through the steps of the installation wizard.
    2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Please report back soon.

I apologize in advance if you have already tried these steps.

Site Moderator

Re: Unable to start Firefox.

For the crashes with Flash, you can check for problems with current Flash plugin versions and try these:

  • disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed
  • disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)
  • disable hardware acceleration in the Flash plugin