Having applied the March Cumulative update from KB2768000 the Central Admin Backup options does not allow selection of a Farm Backup.
There is an option to examine Backup and Restore History - on following this link you get "! You are not a local administrator. You must be a member of the Administrators group on the server that is running Central Administration to perform most backup and restore operations."
The account being used is a domain administrator and for good measure has been added to the local administrators group but still doesnt work.