Nonstop Backup stops

Has anyone else had problems with 'nonstop' backup stopping, refusing to start again and refusing to recognise its backup file, even though it clearly exists? I've now had this happen twice.

I backup from computer to external hard disks, connected by USB. Running Windows 7. A month ago I accidentally discovered the nonstop back in ATIH11 had stopped a month earlier and was no longer backing up. Not only that, but it also said it had NO VALID BACKUPS! Yikes. Now, I know it was working, because I'd had occasion to use it a couple of times and it had restored earlier versions. At which point I'd stopped making regular tests - mistake on my part.

So I upgraded to ATIH12 and went through the whole process of doing backups, including turning on 'nonstop' backup; I also added in online backup.

Lucky I did, because 'nonstop' backup worked fine for about 2 weeks... and then a couple of days ago I suddenly noticed it had quietly stopped again a few days earlier! No notice,no warning, just a little icon in the sytem try.

I tried to start it again. It said it was working and then about 10 secs later turned itself off again. It also said that it had no valid backup. Sheesh! I hunted through the doco, found out how to turn hidden files on and find there is a backup file on the hard disk. But ATIH12 won't recognise it. And won't turn nonstop backup back on (or at least it will, but it just turns itself off again seconds later). It wouldn't even generate a system report when I asked for one. An hour later, it was still 'requesting' that data and I gave up.

My thanks to a forum regular on another post advising someone to use other types of backups instead. I've taken that advice and set up various incremental file backups sooner than rely on the clearly flaky nonstop backup. Pity though - sounds nice, but has been inconsistent and thus unreliable in practice. Have other people had similar issues? And why is it so flaky?