par Darren Dickson.
Hi John,
I have this same problem. It seems to be related to course size. Once your course reaches a certain size (in term of number of activities etc) the backup process stalls. The last time I looked it was an known open job in the Moodle Tracker, so I am not sure there is a solution yet.
My attempts to fix the solution resulted in more problems, so I will be interested if you find a solution.
Darren