Media Grid View never loads

Using word press 4.1.1
But had this issue before upgrading.

When viewing Media Library in admin the default Grid listing does not load. the ‘waiting’ ball just keeps spinning.
If I use list view I see icons and files listed OK.

This effects my ability to insert media into a page as it uses the grid view also to select (and has not other way to view your media ie list?)

If I run a inspector on this page I see this error:
/wp-admin/admin-ajax.php 418 (reauthentication required)

If I look up 418 as a http error you see this defined “418 I’m a teapot (RFC 2324)”

OK. I’m not sure when this started, but was looking into this 2 weeks ago and again today after again updating again to the newest wordpress.

• I have tried using the wordpress to reinstall itself which is does (no errors reported) but the problem persists.
• I have renamed the Plugins folder via FTP to make sure they are not the cause
• I have renamed the Theme folder via FTP to make sure it is not the cause

I also can not use the /wp-admin/export.php to export post when I try to run it.

If I try and download a back up by FTP / phpmyadmin and run it on another domain I get the same issues AND my theme won’t load. If I do a clean install of wordpress on another server it is OK .. but restoring the plugins AND Theme and the theme won’t load .. using Centium – looks like it has some DRM to stop it being copied around. I didn’t set up this site and don’t have the originals to reinstall it.

I don’t think the theme is the problem at all … but I’m nervous about copying up / replacing files in case I stop the theme working as it seems to only run on the live server.