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How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

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New Contributor

How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

Below is the error message window that appears upon start up and (before) the browser tabs appear.


[JavaScript Application] CaptureMovieFox could not be initialized. Some files of the extension maybe missing or there is a problem wit the Firefox. You can try by restarting Firefox.


This problem started after I upgraded to Firefox 5.0.

Edited by a moderator.
If you want a divider line, such as I added during the edit, use 5 hyphen characters in a row.

6 REPLIES
Shooting Star Contributor

Re: How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

Please refrain from using all of those bullets in your post. I messes with the display of your message/question and is unnecessary. Thanks.


I am unable to locate CaptureMovieFox in an internet search. If it is the following add-on, it is only compatible with Firefox 4; that is shown on the add-on page below.

If that is not the add-on,

  1. click Add-ons > Extensions, click "More" next to the add-on name, on the "More" information page, scroll down and paste the homepage shown there in a reply.
  2. Also, from what site did you download the add-on?

Your User-agent shows that you are using Firefox 3.5.8, which is an old, unsupported version of Firefox. To see the User-agent reported with your original question, click "More system details..." next to your original question, then scroll to the bottom of that display and you will see:

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.8) Gecko/20100202 Firefox/3.5.8 (.NET CLR 3.5.30729) 

It is possible that something you have installed has affected your User-agent and that could be causing an error with the add-on, but I am not sure of the add-on you have installed (see above) or the version(s) of Firefox with which it is compatible.

See:




You need to update the following. The Plugin version(s) shown below was/were submitted with your question and is/are out of date. You should update to avoid known security issues with the version(s) you have installed. Click on "More system info..." to the right of your question to see what was included with your question.

  • Adobe PDF Plug-In For Firefox and Netscape 10.0.1
  • Next Generation Java Plug-in 1.6.0_20 for Mozilla browsers
  1. Check your plugin versions on either of the following links':
  2. Update Adobe Reader (PDF plugin):
    • From within your existing Adobe Reader (if you have it already installed):
      • Open the Adobe Reader program from your Programs list
      • Click Help > Check for Updates
      • Follow the prompts for updating
      • If this method works for you, skip the "Download complete installer" section below and proceed to "After the installation" below
    • Download complete installer (if you do NOT have Adobe Reader installed):
    • After the installation, start Firefox and check your version again.
  3. Update the Java plugin to the latest version.
New Contributor

Re: How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

Why would my User-agent say my Firefox version is 3.5.8, when I show that I have Firefox 5.0 installed under "Tools>About Firefox"? How do I fix this and why doesn't automatically get updated when I do an upgrade?


Response from
Your User-agent shows that you are using Firefox 3.5.8, which is an old, unsupported version of Firefox. To see the User-agent reported with your original question, click "More system details..." next to your original question, then scroll to the bottom of that display and you will see:

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.8) Gecko/20100202 Firefox/3.5.8 (.NET CLR 3.5.30729)

Edited by a moderator. If you want a divider line, such as I added during the edit, use 5 hyphen characters in a row.

Shooting Star Contributor

Re: How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

LAST WARNING: Stop being childish immediately with the unnecessary extra lines and bullets or

  • I will no longer respond to you
  • I will report you to the Moderator and ask to have your account and e-mail banned on this forum.

ALSO, edit both of your posts and remove all of that nonsense, NOW!!!

Did you read my post about your User-agent and how to reset it?

Support Forum Moderator

Re: How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

Firefox 3.6 and earlier versions allowed "software" to modify the UserAgent string in Firefox. Too many software developers abused that privilege and some caused problems for Firefox users with the manner is which they did the modifications. The most severe problem caused the UserAgent not to be updated when Firefox was updated, like you are experiencing with it "stuck" at Firefox 3.5.8.

In Firefox 4.0 and later versions of Firefox, software developers can't mess with the UserAgent at all - Mozilla removed all those preferences. But that doesn't fix the UA strings that are carried through during an update, the user has to fix that him/her self.

http://en.wikipedia.org/wiki/User_Agent

type about:config in the URL bar and hit Enter
If you see the warning, you can confirm that you want to access that page.
Filter = general.useragent.
Right-click the preferences that are bold, one line at a time, and select Reset.
Then restart Firefox

New Contributor

Re: How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

I will keep this simple. The other fixes did not fix this problem, which started when I upgraded to Firefox 5.0, and MovieCapture does not work on Version 5.0. Go to Tools on the Firefox menu bar, click on Add Ons. This will open a new tab which lists all the add ons you have installed. MovieCapture should be listed, then simply go to the right and click on Disable. I restarted Firefox to check to see it the error message went away, and it did. Problem fixed.

New Contributor

Re: How do I fix this problem when Firefox starts up? I am running Firefox 5.0.

I had updated to Firefox 6.0 from earlier version, now whenever I start the browser I do not find my saved websites addresses and also all bookmarks gets disappear. What should I do ??