You may use Keychain First Aid to resolve issues in which:
A user's .Mac password is not retained in Internet preference pane, as described in technical document 107097, "Mac OS X 10.2: Won't Save .Mac Password".
Mail and iChat could continue to prompt users for their password after saving it in the keychain.
A user could be unexpectedly prompted to unlock the keychain after changing account information or Home directory location.
Duplicate Mail passwords could appear in the keychain, as described in technical document 106546, "Mac OS X 10.1: Re-enter Mail Password After Upgrade".
Multiple references to the same keychain could appear in the Keychain Access application.
Applications are unable to retrieve items from a keychain file located on a network volume.
Saved passwords could not be read if they were created or modified by certain pre-release versions of Jaguar.
A Keychain dialog can sometimes prompt for permission to decrypt a "(null)" item.