Couldn't load XPCOM | Firefox Support Forum (2024)

I have read through the support forums, and the accepted answer is always the same, to re-install firefox via uninstall, deleting program files folder, and installing again.This doesn't fix the problem.

Not really sure what else to add, except the circumstances of when it first appeared, I have been using it at work for a bi now, absolutely fine, then they gave me admin rights i needed to install other software(which i haven't actually done yet, so not that), and immediately after logging back in with increased rights(same user account), i can no longer launch firefox, due to XPCOM error.(windows 7 64bit)

Chosen solution

What is your computer system and Firefox?

Let’s do a full clean re-install;Download Firefox For All languages And Systems {web link}Save the file. Then;

Using your file browser, open the Programs Folder on your computer.

Windows:C:\Program FilesC:\Program Files (x86)Mac:Open the "Applications" folder.Linux:Check your user manual.

Do Not remove the profiles folder.

Look for, and rename any Mozilla or Firefox program folders by adding .old to them.Do not rename the Mozilla Thunderbird folder.

After rebooting the computer, run a registry scanner. Then run the installer.If all goes well, remove the OLD folders when you are done.

If there is a problem, start your Computer in safe mode and try again.

Starting The Computer In Safe Mode;
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well, As mentioned in OP, i had already done most of this, just leaving:Registry scan -> triedSafe mode -> i don't have bios permissions for that

So followed your guide through, except safe mode part, which was familiar since the only extra step was the registry.

No effect, still get the XCOM error.

Getting Error message couldn't open XPCOM and can't … http://support.mozilla.org/questions/1006494

You need to talk to your tech.

That link, just says the same thing, to clean-reinstall(and cleanup reg) which is what's already been done.

As for my tech, he sits next to me, and between us, we've never seen an issue of granting permissions causing any issues before, so don't really have any suggestions beyond re-installing FF, which is obviously what's been tried, hence me coming here to ask:(

still have no idea why it broke in the first place, but it's working now.Only thing i did different, was this re-install i selected the full download package instead of using the download button on FF homepage, which is a stub (web installer). And installing from full download seems to have fixed it

which begs the question if you have an issue with that? or it's just my system, but the workaround works for me - which is good enough for now:)

Some protection programs don't like the stubs.That is why we recommend the full program.

Hello,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.

I have not previously experienced this in years of Firefox, but suddenly did so.

I followed all the stuff about clearing folders, reinstalling a fresh version 50.0, turning off AV etc etc. The XPCOM error persisted.

I have for a long while been using a free version of Malwarebytes Anti-Exploit, without trouble. However, out of desperation, I turned this off, and, bingo, Firefox started working again.

It doesn't like 50.0, for sure.