Yes, it could very well be a firmware problem. As I mentioned, I think the battery really isn't draining, the Nook just thinks it is. THe problem is that if you have one that is misbehaving, you are at its mercy - if it thinks it needs to be charged, it needs to be charged.
Everytime they have an upgrade, it seems to always include an item that says "better battery life." I keep hoping these updates will fix the way my Touch is misbehaving. So far I've been thru 2 updates and neither has fixed the problem.
