Log-in Window Blank – Updated to 3.1.3

I use a dynamic ip service through no-ip.

With 3.1.2 install my sites were able to use:
– e.g. https://www.example.com (which resolves to e.g. example.no-ip.com)
– use either log-in or register links from https://www.example.com page

With 3.1.3 update, clicking on either the link to the log-in or register page returns a blank window.

If if type in the direct url (e.g. example.no-ip.com/wp-login) all works fine.

Any ideas to get it working how it did with 3.1.2 without rolling back?