Friday, 11 July 2014

Fix “Unexpected Installation Error -203″ Problem While Installing Extensions and Themes in Mozilla Firefox?

Fix it. By following the below mentioned solution 


First make sure you are not using Zone Alarm or CA firewalls as both these firewalls are known to cause this problem.

If you are using any of them, disable it by using its system tray icon and then try to install the extension or theme. Now it should install without any problem. After the installation, you can again enable the firewall.


Most of the times, this problem occurs when you update the Firefox version installed in your system. If you have recently updated Firefox version, then delete following 3 files from your Mozilla Firefox Profiles folder:



If the above solution doesn't work, then its a problem of corrupt profile folder. Sometimes your existing Firefox profile folder gets corrupted and causes this problem. You'll need to create a new default profile to fix this problem. But it might remove all your installed add-ons.

1. Open Firefox Profiles folder as mentioned in the link given in METHOD B. Don't go to the "xxxxxxxx.default" folder, go one folder back and you'll see a file "profiles.ini" in the same folder where "Profiles" directory exists. Either rename or delete the "profiles.ini" file.

2. Now double-click on "Profiles" folder and delete "xxxxxxxx.default" folder. Make sure to take its backup if you want to save your bookmarks, cookies and passwords later.

3. Now run Firefox again and it'll re-create the default profile folder and will work like you installed it for the first time. It'll fix the problem.


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