iCloud doesn't backup and Photostream not working
I have an iPhone 4 and my wife has a 4S. My iCloud backs up and Photostream works correctly, but my wife's doesn't. Everytime we initiate an iCloud backup it fails. It also fails when it initiates automatically.
Also, any new photos taken are not uploaded to Photostream.
I know I have set them up correctly because my phone works. Any ideas would be appreciated.
iPhone 4, iOS 5