I used to have a Kindle 3 (keyboard). After almost 3 years of honourable service, it started getting stuck more and more, until reset wasn't solving anything anymore.
The very helpful Amazon customer service replaced it (albeit out-of-warranty) with a Kindle Touch. Happy again, I copied some books I was reading to the new device and started reading.
After less than a month, the Touch got stuck too. Now since I don't believe in cursed ebook users, I'm trying to figure out if there is a common cause. I haven't treated any reader badly, always charged before getting the warning, never let it fall (at least the new one).
I'm starting to suspect it's because of some book I loaded, can it be? I usually use Calibre on Windows 7 to manage ebooks.