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On startup Firefox says "couldn't load XPCOM"

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New Contributor

On startup Firefox says "couldn't load XPCOM"

My desktop is running Windows 8, which recently crashed. Since then, every time I start up, Firefox 17.1 (which is in the startuo folder) does not load, but brings up an error window saying (Couldn't load XPCOM). Dismissing the window then allows me to start Firefox myself. I have uninstalled Firefox (but not the personal stuff), downloaded a new copy of Firefox 17.1 and re-installed.... same thing happens.

Just to clarify ..... this only happens once, following the initial boot up of the desktop. I dismiss the error window and all is well after that.

Any bright ideas please?

What is XPCOM referring to? A missing dll file? can I find this file elsewhere and move it to the correct location?

Many regards.

1 ACCEPTED SOLUTION

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New Contributor

Re: On startup Firefox says "couldn't load XPCOM"

Thanks again for all the responses. I have now put Firefox back into my Windows 8 startup folder and rebooted. All is fine, Firefox (and Thunderbird) starts as it is supposed to and there is no sign of an XPCOM related error message! So .... I would have to assume that the problem was (somehow) caused by the crashing of my Windows 8 and that (somehow) removing Firefox from the Win 8 startup folder, rebooting, then putting Firefox back into the startup folder, and then rebooting, has put things back where they used to be. Somewhat strange, but hopefully the above may be of use to someone else with a similar problem in the future. Many regards to all.

21 REPLIES
Senior Contributor

Re: On startup Firefox says "couldn't load XPCOM"

Interesting that it only happens once during startup. Did you add Firefox to the startup folder yourself? What happens if you remove that link, does the error message go away?

New Contributor

Re: On startup Firefox says "couldn't load XPCOM"

Thanks for an interesting response. Yes I did add Firefox to the startup folder myself as I could not find any way of getting Windows 8 to do it for me! I'll remove the link and reboot and see what happens!?! Will post back later today. Many regards.

Site Moderator

Re: On startup Firefox says "couldn't load XPCOM"

Note that there is also a Firefox 17.0 ESR version for testing purposes that will become the next ESR release in February next year.

Did you do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox?


Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

  • Do not click the Reset button on the Safe mode start window or otherwise make changes.
New Contributor

Re: On startup Firefox says "couldn't load XPCOM"

Well I have removed Firefox from my start folder and the error message no longer appears - even when I first load Firefox. So that would appear to vindicate the Firefox installation .... now I will have to put Firefox back into the start folder to see if the error re-appears or if the problem was just a result of my Windows crash. Will post the results after I have had time to do the above. Many regards.

Senior Contributor

Re: On startup Firefox says "couldn't load XPCOM"

If this error only happens when you put a shortcut to Firefox in the startup folder, it would appear that there is something called XPCOM that needs to finish loading before Firefox can load. I have honestly never heard of that problem before, so if that's the case, we should file a bug about it since it seems Windows 8 specific (I have no issues adding a shortcut to Firefox in my Windows 7 startup folder).

Please let us know the end of this story!

New Contributor

Re: On startup Firefox says "couldn't load XPCOM"

Thanks again for all the responses. I have now put Firefox back into my Windows 8 startup folder and rebooted. All is fine, Firefox (and Thunderbird) starts as it is supposed to and there is no sign of an XPCOM related error message! So .... I would have to assume that the problem was (somehow) caused by the crashing of my Windows 8 and that (somehow) removing Firefox from the Win 8 startup folder, rebooting, then putting Firefox back into the startup folder, and then rebooting, has put things back where they used to be. Somewhat strange, but hopefully the above may be of use to someone else with a similar problem in the future. Many regards to all.

Senior Contributor

Re: On startup Firefox says "couldn't load XPCOM"

Glad to hear that the problem is solved! Yes, it is somewhat strange, but computers in general can be a bit of a mystery sometimes. Please come back to support.mozilla.org if you ever have another problem with Firefox. Cheers!

New Contributor

Re: On startup Firefox says "couldn't load XPCOM"

I have a similar yet worse problem. XPCOM couldn't load error pops up every time I start firefox. any help?

Site Moderator

Re: On startup Firefox says "couldn't load XPCOM"

Do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

Download a fresh Firefox copy and save the file to the desktop.

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

  • Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

If you keep having problems then also create a new profile.