I’ve got an account set up on Escargot, which is indeed set up to work with older versions of MSN. Have done the registry hack. Still fails. Using correct email and password.
That said I created my account like 20 minutes ago, so most likely it is an issue with the amount of time needed to pass, but I doubt it.
Using Windows Messenger included with Windows XP and MSN Messenger 7.5 prepatched and neither of them work.