"Download Failed. Forbidden", when updating Upfront


I had a notice to update Upfront today, so I clicked on the button in the attachment inside my WPMU dashboard area in WP. It then came up with the attached error message. saying 'Download Failed. Forbidden.'.

In addition, now at the top of almost all pages on the website it says:

"Unknown element type: PostDataUnknown element type: PostData" and the pages do not display properly.

This is requiring urgent attention. Support access has been granted.

Many thanks,