Reports of iBook startup and disk corruption problems on Apple's Tech Exchange

There are several threads in Apple's Tech Exchange on blinking question mark startup problems and/or unrecoverable hard drive damage on iBooks. Most commonly, the problems begin after a wake-from-sleep crash. In some cases, Disk First Aid reports an "Invalid BTree node size" error and says it cannot repair it. Unfortunately, the way Apple's Tech Exchange works, the problem may be not as widespread as it looks: the same messages/threads get listed repeatedly. One user in particular (Lynn Joiner) is responsible for many of the messages on this topic. However, we did find a reply from Apple Support on this matter: "We've been investigating the reports of this symptom, but I don't have any solutions to share yet. It's possible that replacing the drive may be necessary, and the 90 day warranty only applies to phone assistance, not with hardware problems. You have a 1 year warranty for hardware. That does not mean it is a hardware problem, nor does it mean that replacing the drive is a definite fix. As I said, we are looking into it to find the real cause/fix."