This was Fixed in Blogs Phase 2.1 Release Tuesday 24th February

Since the upgrade to WordPress 4 we have a problem with password protected post.

Viewing a password protected post redirects the user to RM Unify authentication if not logged in and to a SAML2 error code if already logged in.
This behaviour exists regardless of Blog privacy level.  This means that password protected posts cannot be accessed.

The Developers are looking at fixing this issue as soon as possible.

There is no real workaround for this at the moment, other than not using password protected posts.  There are serveral option that will partially workaround the problem:

A workaround for people who don’t mind the material being publicly available is to remove the password protection:

1. Go to each post which is password protected
2. Edit the post and…
3. Add a tag to them “password protected” (so they can be found again afterwards)
4. In the “Publish” box on the edit page for that post, click the “Edit” link next to “Visibility”
5. Click the blue “Update” button

A workaround for people who don’t want the material to be publicly available, and can make their entire blog Glow Only (i.e. visible to logged in Glow Users only) is to:

1. Go to Settings > Reading
2. Scroll down to “Blog Visibility” and set this to “Glow Only”
3. Click “Save Changes”
4. Go to each post which is password protected
5. Edit the post and…
6. Add a tag to them “password protected” (so they can be found again afterwards)
7. In the “Publish” box on the edit page for that post, click the “Edit” link next to “Visibility”
8. Click the blue “Update” button

To reinstate the password protection when the fix is deployed:

1. Go to the WP Admin Dashboard
2. Click “Posts” > “Tags”
3. To the right of the “password protected” tag, click on the number in the “Count” column… this will show all posts with this tag
4. Edit each post and add the password protection back again