"the last backup could not be completed"
I noticed my iPhone 3GS has stopped backing up (It is connected to a power source and has WiFi connection).
I tried to manually back up to iCloud, but I get the following message after several minutes; "the last backup could not be completed."
Today, I restored my iPhone and downloaded iOS 5.1. I still have the same issue. I deleted the old backup in iCloud and tried it again - and still the same message.
Any ideas how to solve this?