I have been using iBooks for some time now, without problems. However, my most recent purchase does not seem to sit well with my iPad (1st generation). The book downloads to my library fine, but when I go to open it, it invariably crashes after approximately 20-30 seconds. I have redownloaded the book several times, reinstalled iBooks and restarted the device. All other books open fine on the iPad, and the book in question also opens fine on my iPhone 4. Any ideas an what is causing this? ETA: both devices are running iOS 5 Beta, but I don't think this is the problem, as it is localised to one specific book.