Try the Firefox Safe Mode to see how it works there. The Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• You can open the Firefox 4.0+ Safe Mode by holding the Shift key when you use the Firefox desktop or Start menu shortcut.
• Or use the Help menu item and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Don't select anything right now, just use "'Start in Safe Mode" To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before using the Firefox shortcut (without the Shift key) to open it again. If it is good in the Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one.

Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.

if your flash 11, downgrade to flash 10.3

Also make sure that your security software (firewall, anti-virus) isn't blocking the upload.

How to down-grade?

Still doesn't work in safe mode and also after follow every steps in the trouble-shooting procedures.

Sigh..........

Try this

1. Type about:addons in URL

2. Make sure "Shockwave for Director" is present

3. find "Mozilla ActiveX Control and Plugin Support"

4. disable it

5. refresh the page

in the "get add-ons" page, cannot see "shockwave for Director" and "Mozilla ActiveX Control and Plugin Support"

You do not need the Shockwave for Director plugin as that plugin is hardly used these days.

You do however need to update your Java 1.6.0_31 version as that version is seriously outdated.

Hi I can not attach files in yahoo email. I am using Firefox 20.0 I am on win 7. I have turned off AVG antivirus, firewall, started in safe mode, uninstalled fire fox uninstalled yahoo Browsers plus. Reinstalled yahoo browser plus. None of these has worked. Anyone have any idea? It does work in IE perfect.

I THINK FIREFOX IS NOT A VERY GOOD BROWSER AT ALL. IT IS A SHAME I USED TO THINK IT WAS THE BEST AROUND. IM STILL HAVING THE SAME PROBLEMS. DOES NOT LOOK LIKE THEY CARE AT ALL. STAFF HERE HAS NOT RESPONDED. WHAT A WASTE.

I also have the same problem, I followed all of the suggestions here and I'm still in the same place: Cannot upload/attach files to yahoo mail Hopefully someone can figure this our for us. In IE, no prob. Right now, I am trying to update Adobe, and it won't update. Maybe they're related....

yes i have done that

I have tried everything and still doesn't work. I have given up and switched back to old version of yahoo! mail. Everything is working fine now buy without the new features of the new version. Sigh.....

While I can attach and send files from Yahoo mail, I can no longer forward attachments which come in received email. Started with FF 20. Now using FF 21.0 same problem. Forwarding emails with included attachments works fine on IE8. Am using XP.

Tried all suggestions, nothing worked. Please! I'm loyal to Firefox from it's first release, but this will eventually necessitate leaving FF unless a fix is issued with some promptness.

I have found a solution Anyone who is getting the error of not being able to attach a file, no matter what the size, in Yahoo using Firefox (and apparently certain older versions of Internet Explorer):

Update your JAVA to the latest version (Version 7, Update 25), and uninstall any older versions. Just for anyone's interest, the version that was failing was Version 7, Update 10.

I got a friend's computer to work using this. Hopefully it will work for you as well.