The reboot key-combo is "shift-alt-r". After a couple of soft-resets I tried a reboot and it worked! woo!
No, it isn't the case causing crashes in my case, it's my own converted-from-chm-emailed-to-my-kindle ebook.
Edit: update, she's working again now that I'm done writing this post. Perhaps it was just really really busy finding that page?