by Ken Task.
@Tony ...
Did you check system defaults for backups to make sure user data is not locked out?
What version of Moodle? Got command line access? In moodlecode/admin/cli/ there is a script called 'backup.php'. Execute like: php backup.php --courseid=[CID] --destination=/home/m26backups/
Have any clues in moodledata/temp/backup/? Any larger than 0 byte .log file contains info that might provide a clue.
'spirit of sharing', Ken