Yahoo team released an updated version of Yahoo! Messenger 9.0. This latest build (version 220.127.116.118) includes a fix for the sign-in issues that have been affecting some users.
If you were seeing an error code 81003005 when trying to sign in, this latest version should fix that problem. Even if you were experiencing a different kind of sign-in issue, Yahoo tean recommen dinstalling this latest version.
Download Yahoo Messenger 18.104.22.1688