The error “Couldn’t load XPCOM” is usually caused by Windows Updates. Though there are several methods on the internet to fix the issue the one in this guide is by far the easiest I’ve found.
In order to proceed with this method, you will need to use Internet Explorer (that is there by default, or another browser if you have it installed)
If you cannot locate/find Internet Explorer, simply Hold the Windows Key on your keyboard and press R to open the run dialog, and in the run dialog type -> iexplore.exe and click OK.
Method 1: Simply Upgrade/Reinstall
This method has worked for most of the users and it is very easy to follow. Once you’re in Internet Explorer or another browser, simply head over to the following address to download the latest setup file for Firefox, run it and install. https://www.mozilla.org/en-US/firefox/new/?product=firefox-3.6.8&os=osx%E2%8C%A9=en-US
Method 2: Back up and do a Clean Install
Before you begin, if you would like to Back Up Firefox and you can also choose to export certain things such as your history, passwords or bookmarks and you can import these bookmarks later from Chrome or other browsers.
1. Download the 30-day trial version of RevoUninstaller by going to www.revouninstaller.com and clicking the following button on the site
2. Now you should have the Revo setup file, open it and install it. After it has been installed, you will have the RevoUninstaller icon on your desktop. Open Revo Uninstaller, and select Firefox,
3. Now click Uninstall and then select Advanced and follow the prompts on the screen to uninstall Firefox.
4. Then select Advanced and Click Scan on Revo Uninstaller.
5. Next screen will present you with Leftover files, see the screen below, select all of them and click Delete.
6. Then, go to C:\Program Files first, and delete the Mozilla Firefox folder and also check C:\Program Files (x86)\..
7. Press “Windows’ + “R” and type in “%temp%”.
8. Press “CTRL” + “A” and then press “Shift’ + “Delete” to clear this folder.
9. Reinstall Firefox and check to see if the issue persists.
Note: If this is happening on the Tor browser, run it as an administrator and try disabling your antivirus temporarily. It is also recommended to uninstall Geforce Experience if you have it installed on your computer because it is known to cause conflicts with the application in certain cases.
Method 3: Run as Administrator
In some cases, the issue is simply fixed by running the browser as an administrator. Administrative Privileges are required by some Softwares to pass certain hardware/security limitations. Therefore, in this step, we will be running the browser as an administrator and then check if that fixes the issue. For that:
- Right-click on the browsers executable on the desktop.
- Click on the “Properties” option and then select the “Compatibility” tab.
- In the compatibility tab, check the “Run this Program as an Administrator” option and click on “Apply” and then on “OK.
- Run the browser after that and check to see if the issue persists.
Method 4: Using Firefox for Tor Network
In some cases, this issue occurs with the Tor browser and doesn’t seem to go away using any workaround/fix. Therefore, in this step, we will be using the Firefox browser to connect with the Tor browser instead of the Tor browser itself. This fix works for most users and is really easy to apply. In order to do so:
- Download and install the Mozilla Firefox browser from here.
- Now, navigate to the Tor browser installation folder which is usually on the desktop and its address should look something like this.
Desktop\Tor Browser\Tor (full path "C:\Users\your-username\Desktop\Tor Browser\Tor")
- There should be a “tor.exe” at the bottom of the folder, right-click on this executable and select “Pin to Taskbar”.
- Now, startup Tor and wait for it to fully connect to its network.
- After Tor is started, launch the Firefox browser that we just installed not from inside the Tor bundle but the standalone browser that we installed in step 1.
- Click on the “Setting” icon on the top right of the Firefox bar and select “Options” from the list.
- Click on the “Network” tab and then select the “Settings” option.
- Click on the “Manual Proxy Configuration” option and enter the following line there.
SOCKS Host: 127.0.0.1 Port: 9050
- Click on “OK” to save your changes.
- Type in “About:config” in the address bar and verify the “I’ll be Careful” prompt.
- Type in “network.proxy.socks_remote_dns” in the search bar and toggle it to be TRUE.
- Restart Firefox and enter the following in the address bar.
- It should now say that you are configured to run Tor.
- The issue should now be fixed completely.