First find the location of the keyring.
find . -print | grep -i 'login.keyring'
Now delete the login.keyring file.
rm ~/.gnome2/keyrings/login.keyring
The file above can be on a different location in your case.
The next time when you want to save a password in a keyring it will ask you for a new password first.
Please be careful, all other passwords in the keyring are gone when using the above option. See link
for more possibilities.
