I've seen similar issues, but nothing so far like mine.
My iPad is giving me that pop-up that says iCloud is full and can't sync. When I visit the iCloud managment tools, it says that I am currently using .2 gigs out of 5. I should have plenty of room. Additionally, the little green bar at the bottom is showing a small sliver of used data. Why is the iPad telling me it's full and can't sync?