Gnome Keyring keeps asking for a password that doesn't exist

It only comes up on auto login actually. To get rid of it :

• Open seahorse (aka "Passwords and Encryption Keys" in the preferences menu),
• Right click on "Passwords: login" (the first entry in the list),
• Change password : "Old Password" is your user password, then do not type anything in "Password" and "Confirm",
• then "Ok" and there will be a warning : "Use Unsafe Storage"