Ubuntu : How To Remove Password Keyring

1. Open up your Home Folder by clicking Places>Home Folder
2. Press CTRL-H (or click View>Show Hidden Files)
3. Find a folder called .gnome2 (it has a period at the beginning of the name) and open it by double clicking on it
4. In side of the .gnome2 folder, there is another folder called keyrings. Open it up.
5. Delete any files you find within the keyrings folder
6. Restart the computer

from : http://davestechsupport.com/blog/2009/01/16/how-to-remove-ubuntus-password-keyring/

or

rm ~/.gnome2/keyrings/default.keyring