Are there specific actions that cause the formatting issue to happen? For instance, turning the device on, changing pages, etc?
Also, I know the book itself is in main memory, but do you have a memory card in the device?
I'm not sure what else you've tried to fix the issue, but a "paperclip in the hole in the back" reset might be useful.
Besides that, you could use the flasher to revert back to the original firmware. There are instructions in the main flasher thread.
Your third option may be to call Sony and see how they can help you. You never know, they might actually be able to help.
