Preview button fails to deliver post or page

We are running WP 4.1, with multiple networked sites at reframe.sussex.ac.uk
and the preview function for both Pages and Posts on sites across the nextwork fails to deliver a preview of the page.

The button delivers a url which would be the permalink for the page, without ‘preview=true’, as one might expect.

The site retuns a 404 error page, regardless of whether the page is new, saved as draft or an existing page which has been edited.

I have checked the forum and cannot find any similar issue wiith 4.1. Has anyone else seem a similar issue?