The automated backups seemed to have stopped, it isn't that they are failing to finish, they aren't even getting started.
I've checked the usual suspects - the cron is fine, runs as usual. There is plenty of space on the server. The permissions on the moodledata/temp folder have not changed. The auto backup is defintely set to run. I've checked the settings in the database are all still present and correct.
I've stopped a Moodle 2 that was also on the same server backing up just in case it was hogging all the resources, no impact.
It is almost like the bit that makes it go, has gone. Other than the cron and the backup active setting in the databse I don't know what makes it go.
I have several Moodles on the same server. Half are backing up fine and half are not. It isn't falling into all those one side of midnight or the other, it is a mixed bag. It is all really odd.
There is nothing in the php error log, nothing in the IIS log files and when I set a cron to produce a log file all it seems to indicate is that there is nothing in it to do with backups.
I've tried turning the backup off on one and then back on again a few hours later to see if it provokes it into action - nothing.
I've run out of ideas now.