The iCloud backup of my iPad 2 running IOS 6.0 has suddenly stopped working. The last automatic backup attempt resulted in a message saying "the last backup could not be completed". Previous automatic backups worked well. I tried a manual iCloud backup a couple times with similar results. The little spinning wheel labeled "backing up" was rotating, but the blue status bar not progressing and the message underneath saying "estimating time remaining". After a half hour or so of this, the backup attempt stopped and "the last backup could not be completed" message came on. Previously, manual backups worked fine and took about 10 minutes. My backups are modest in size (about 450 MB) and I have 4.5 GB of free space in my iCloud storage. Syncing of the iPad to my iMac via iCloud (Contacts, Calendar, etc.) is working just fine. Any ideas?