Sending of password did not succeed. Mail server incoming.yahoo.verizon.net responded: (#MBR1212) Incorrect username or password.

I suddenly get the following error message when I try to access my email using Thunderbird: Sending of password did not succeed. Mail server incoming.yahoo.verizon.net responded: (#MBR1212) Incorrect username or password. I have checked the username and password and they are working using my webmail. I have tried deleting the saved passwords from Thunderbird, logged out and logged back in and entered the password. It still does not work. My son is also having the same problem with his account.