Somewhere around July 30th, my iCloud backups started failing. I got the ‘Backup cannot be completed message’. I am running a beta of iOS 6, so I assumed it had something to do with that. After some research, I discovered it in fact had nothing to do with iOS 6. It took some trial and error, but here is how to solve it:
- Turn off iCloud backups and delete any partial backups
- Make a good iTunes backup (just for kicks)
- Turn iCloud backups back on, but turn off every single application
- Make a full backup to iCloud
- Assuming step 4 works, turn on a few applications
- Make another backup
- Once it fails again, further test the last set of applications you turned back on.
- Once you discover which app it is, figure out a way to delete the application without causing a ton of pain (export data, etc)
On my iPhone, the cultript was Keynote. On my iPad, it was iA Writer.