firefox add-ons.jpgEver since we launched the CyberSearch extension I’ve been getting a ton of emails with recommendations on what I can do to make it better, and alongside those emails are also a few dozen from people who are having troubles trying to install it. What happens to them, and I’ve had this happen to me before, is they are prompted with this warning when trying to install the extension:

Firefox could not install the file at [URL] because: Invalid file hash (possible download corruption) -261

Believe it or not this has been a known problem for quite some time, and there are a couple of different things you can try to circumvent the problem.

  1. Clear your cache. Go to Tools -> Options -> Advanced -> Network / Offline Storage -> Clear Now and then try reinstalling the extension.
  2. Enable third-party cookies. A few commenters (thanks Clark!) have pointed out that enabling third-party cookies in Firefox is also something you should do to get around the error message. To do this go to Tools -> Options -> Privacy and check the Accept third-party cookies box.
  3. Manually install the extension. The easiest way to do this is to just download the extension in another browser, and then drag the downloaded file into the Firefox window. This should initiate the installation process.
  4. Suspend ThreatFire. I’m adding this one to the list because several of our commenters (thanks Sunny!) have pointed out that ThreatFire could be one of the reasons that extensions won’t install. Temporarily suspending ThreatFire should solve the problem.
  5. Temporarily disable your antivirus. When all else fails the culprit could be that your antivirus application is preventing the installation of the extension. This is kind of a last resort, and not something that I really recommend doing.

Again, I apologize for those of you having issues installing the extension, but there is a light at the end of the tunnel. Once we manage to get enough (hopefully positive) reviews of the extension we will be able to get CyberSearch out of the experimental stage. From what I’ve read after that happens the “invalid file hash” errors shouldn’t really happen anymore. So if you’ve got a spare second go drop by the Mozilla site and leave a review for our extension.

There Are 15 Comments

  1. If you have this problem you should also try deletting these 3 files from you firefox profile folder :
    extensions.ini
    extensions.cache
    extensions.rdf

    Profile location :

    Windows XP : C:\Documents and Settings\[User Name]\Application Data\Mozilla\Firefox\Profiles\
    Windows Vista : C:\users\[User Name]\AppData\Roaming\Mozilla\Firefox\Profiles\

    Make sure Firefox is closed when deleting these files.
    Firefox will regenerate these files on restart.

  2. I have this problem when I try to install extensions while the popular ThreatFire security program is running. I just right-click in the taskbar and “suspend” while I install the extension.

  3. Thanks so much for this post. I’ve been having this problem with other extensions and had no idea what to do. It is probably the cache problem on one machine. On the other is probably the ThreatFire program that Sunny commented about. Thanks Sunny. I don’t know if I would have figured that one out.

  4. I spent several evenings trying to get add-ons to work with Firefox 3 before realising ThreatFire was to blame.

  5. Sunny wrote:
    I have this problem when I try to install extensions while the popular ThreatFire security program is running. I just right-click in the taskbar and “suspend” while I install the extension.

    Thanks Sunny! I’ve added that to the list. I haven’t used ThreatFire much so I wouldn’t have guessed that it would cause a problem.

  6. After trying all of the above unsuccessfully, I traced through the linked bug and found a suggestion to enable 3rd party cookies (which I had disabled). That was the trick for me – it installed fine after I did that.

  7. Clark wrote:
    After trying all of the above unsuccessfully, I traced through the linked bug and found a suggestion to enable 3rd party cookies (which I had disabled). That was the trick for me – it installed fine after I did that.

    Thanks for the info Clark! Glad you got it installed.

  8. Enabling third party cookies did it for me as well… add that to your list ! :D

  9. Tommy wrote:
    Enabling third party cookies did it for me as well… add that to your list ! :D

    Thanks, we’ve added it to the list since more than one person has confirmed this as a possible problem.

  10. I had the same problem downloading the extension. I noticed that when I did a “right-click, save-as” to try saving the .xpi file to disk, I instead got a file called ‘login’. It’s as if the login didn’t work, and it’s trying to get my to login in again. Making a new profile, logging in there, right-clicking and saving the .xpi to disk from there and then loading it in the original profile worked for me.

  11. I have to say that TEO’s post about deleting the extensions files worked like a charm. Thanks so much!

  12. i’ve tried everything that you’ve written here, even “solutions” from mozzila, nothing works. I’ve disabled ESET smart security, spybot search and destroy, deleted the 3 files, allowed cookies, everything. No result. I even reinstalled firefox. Still, no result. And i have Windows XP SP3 up to date. I’m starting to lose my patience and throw my pc out on the window x(

  13. The “enable third party cookies” did it for me. Yay! Thank you so much, guys!

  14. After reading this and nothing was working, I took an educated guess from Chris’s information and came up with a solution. What worked for me was signing into my account on Mozilla’s addons sight. :D If you don’t have an account, register one, then sign in.

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