I have been using my iPad 2 for over 6 months, and one of the first apps I purchased was Penultimate. I have synced Penultimate with Evernote and Dropbox because I also have a work iPad 2, and I wanted to be able to share the notebooks with both iPads. Everything has been working well, until just this week. When I ask it to back up my notebooks to Dropbox, I receive this message "This operation could not be completed. Your iPad disk may be full." I don't even know where to check into this. I have looked at my storage, and I am just at 50% space on my iPad, and only 5% on my Dropbox, so I am thinking it is referring to something else. What could this be?