Ever since the WordPress 4.1 upgrade we have

Ever since the WordPress 4.1 upgrade we have been experiencing problems with mapping domains.

We are able to map the domain successfully however when trying to access the mapped domain (the fqdn) we are redirected to the WordPress Registration is Disabled page.

We have a hundred or so mapped domains that have been working fine for years... I have seen this problem now on two different networks.

JL