My Kindle is rather old, and I have a lot of titles on it. Is that why it always crashes when I go online (usually I set it to airplane mode unless I want to shop)? I get Application Error messages multiple times, the system is extremely slow, or it crashes altogether. Sometimes, I need to restart, and when I do, the software updates, like it is doing right now, unprovoked; it just shut down and rebooted by itself. Something is clearly wrong. It's become a real hassle to acquire new titles.
Which Kindle do you have, and how much free space is on the device?
You might try rebooting: Make sure it's charged, unplug it, press and hold the power button in for a full 30 seconds (time it, and ignore prompts), then release and leave it alone for a few minutes while it restarts.
try taking some of the books off - most people recommend keeping 2-300 books max on it. All the books you purchased from Amazon are stored on the Amazon servers and you can redownload them at any time.