unable to unlock login keychain?
If you cannot unlock the keychain then its contents are lost, they're encrypted using the keychain password.

Your login keychain and password are linked, if the login password is changed via system preferences the keychain password is changed to the new password also. However, it is possible that the login password can be changed by other means whilst not changing the keychain password.

When the system logs in it will try to unlock your keychain with the same login password - if they don't match, you'll see the error message you're seeing.

If you manage to remember the keychain password and unlock the keychain you should change your login password to match. But, as I said initially, you're out of luck if you can't remember the password.