I had posted a fix to an issue that I was having with my iPhone 3GS (it was randomly shutting off) that I thought I had taken care of, however, just this morning, when the battery had about 70% power, it just died, and I couldn’t revive it.. The last app that I was using before it died was the Photo app. The reason I mention that is that when I was doing my research on this, I read on a forum that the last thing that another person was doing before it just shut off was emailing a photo from the Photo app. It could be a coincidence, but I just figured I would mention it.
So, I did some more research and found a fix!