Looks like Apple is having a tricky time of things this morning: its iCloud and iMessage services are currently experiencing difficulties.
The hiccup means that users are having problems with Photo Stream, iCloud documents, back-ups, iPhoto journals and iMessage. So, if things aren't quite working properly this morning, it's not you — it's Apple.
It's not clear yet when normal service will resume.
Update: Annnnnnnd we're back. [Apple]