Error backing up files & database

Hi,
for the last four weeks or so I have been unable to backup my site.
Backup fails whether I do a full backup or backup the files and database individually.
Wordpress and the plugin are both updated to the most recent versions.
I don’t want to have to resort to another backup plugin but I need regular backups.

Thanks in advance.

The page I need help with: [log in to see the link]