Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

Thank you! Disabling hardware acceleration fixed the problem. Doesn't seem like there is a graphics card update available, so I'll just keep this disabled for now.

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.

Did you try to reboot the computer (always the first to try)?

I'm not sure why hardware acceleration would have an effect on uploading files.

I have been having the same problem. The file upload just makes Firefox not respond where I ultimately have to close the program and restart to use the browser at all. I can upload on every other browser. The problem DOES occur in Safe Mode. So what do I do now?

I have the same problem. I have tried all their fixes. Need new input. Thank you.

Hi jrmcmahon! If the above information does not resolve your issue, please consider creating a new thread containing the specific details of your issue.

Doing so will allow the Mozilla volunteers to give you solutions that are more helpful to you. This may help them to solve your problem faster and more efficiently.

Please, feel free to post the link to your thread on this thread for volunteers interested in assisting you.

Thank you.

Thank you, Wesley. I thought I had started a new thread. And I have tried all the recommended troubleshooting. Nothing works. After using Firefox for years and years, a software upgrade came along and Firefox began to crash, after a while, it ran but this upload issue began to occur.