When I receive the "Cannot generate SSPI context" it is when my domain account is locked out for some reason (another story) and cannot be authenticated. Was the change of Service Account part of other changes in the Active Directory archetecture? Is the service account and your account in the same domain, and if not, is there a properly configured trust? Did you recently reset your password and might there be a service or email app somewhere that tries to login with your old password and locks up your account?