I recently migrated data from an Active Directory user account to a new user account, due to a bungled unbind from the Active Directory. Inside the new user account, I was able to import the login.Keychain, but the System.keychain was read only. I’m not sure if this is the correct permissions for the System.keychain, but I fired up Terminal and ran the following:

bash-3.2# sudo chmod 644 System.keychain