I have an iPod touch 3G with iOS4. I was on 3.1.3 JB before going to iOS4 but I did a full shift-click restore, and then update (not from backup). Anyways, this morning when I woke up, I loaded up the net on my iPod and was checking out some PSP stuff and Facebook and all that jazz. The iPod then died on me (10% bat when I woke) and I put it on my wall charger. I went and ate breakfast and came back upstairs to check facebook again. So after looking at that for a few minutes, I slept it and slipped it into my shorts pocket. I did a race on Gran Turismo (PSP) and pulled my iPod out of my pocket. I tried to press the sleep button and the home button to no avail, the screen did not turn on. I plugged it in to my wall charger and nothing happened. So I held the Home button and the Sleep button together until the Apple logo came back up. So, I thought it was just a once and done thing. However, around an hour later, it did it again after I put it in my pocket, slept, for about 20 minutes. It seems like it is going to hibernation or something. I'm going to try leaving it on the charger and give a full charge and see what happens, otherwise I'll just backup and restore.