NOTE: Mozilla support members will never as for any personal information (i.e. Email). You can remove your email address from the question.

Ensure that you have verified your sync account, via email message.

I have also attempted to reset my password via email which sent me an email while attempting to fix the issue today. That was the only time I have received any email from Firefox. Other than that, I have not received any form of email communication from Firefox. However, as previously stated, I can log into my "Account Management Portal for Mozilla services" on the Firefox Sync website. The problem still continues.

How do I further verify my account through email and solve the sync error?

Clear the cache and the cookies from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Try Firefox Safe Mode to see if the problem goes away. 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 Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in 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.

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

Please report back soon.

I had this problem, but fixed it. The culprit was custom privacy/history settings that were set to clear saved passwords on exit, i.e:

Options > Privacy > History > "Firefox will: Use custom settings for history" > "Clear history when Firefox closes" > Settings > Data > Saved Passwords

This made firefox clear all saved passwords (which is generally what I wanted, as I use LastPass for password management), including the Mozilla Services Password (which is NOT what I wanted, as I still want to use Firefox Sync).

To see if you're having the same problem:

1. After setting up sync, make sure that you have two lines in Saved Passwords (which you can find under Options > Security > Saved Passwords) starting with "chrome://weave" and mentioning Mozilla Services.
2. Restart Firefox and check if the Mozilla Services passwords are gone. If they are, check if you have the same custom privacy settings that I have.

For the devs: If I may suggest a solution, I would make the Mozilla Services password entries excempt from the clear-saved-passwords option. (Yes, I realize that adding exceptions to the rule, like this, is probably easier said than done.)

I have the same problem, and have noticed the password saved in the browser list has an extra character which I cannot reproduce on my keyboard in it, I am able to retype the password and log in ok, but whenever it syncs the passwords this extra character gets added causing the password to be refused on subsequent occasions, I have even deleted sync and started from scratch only to find this same character gets added to the password saved in the list.

It always seems to be in the 4th letter and is a capital A with ^ sitting on top.

I too have never had an e-mail to verify the account.

Are you using any special accented characters?

This  character is usually an indication that an Unicode character is presented as its combining characters.

I have only used standard keyboard letters, Caps, punctuation and numbers etc, no specials unless £ is a unicode caracter, but that appears in the password field as expected. (the saved password is 1 character longer than the correct password)

After the error occours, clicking update allows the correct password to be entered, and allows me to sync, but it doesn't actually update the password in the saved password list in firefox. This still remains the same, so next time I log in the error re-occours. I can live with it but it needs correcting.

I have also reinstalled the whole OS and synced correctly once without the error but on next login the error occours as the incorrect password is saved in the synced data overwriting the new data in the browser. I had just typed in by hand.