3.1 admin login problem

Replace the Authentication Unique Keys/Salts within your wp-config.php file in your blog directory. See these instructions and URL to do so:

https://api.wordpress.org/secret-key/1.1/salt/

/**#@+
 * Authentication Unique Keys and Salts.
 *
 * Change these to different unique phrases!
 * You can generate these using the {@link https://api.wordpress.org/secret-key/1.1/salt/ WordPress.org secret-key service}
 * You can change these at any point in time to invalidate all existing cookies. This will force all users to have to log in again.
 *
 * @since 2.6.0
 */