I've had this issues as well, and saw that someone suggest that reformatting the SD card may help. Backed up my stuff and did this. No change. Went to Sprint and told them not to do a factory restore. Was told it would take an hour to get done. Came back and was told that bc they can't do a restore, they can't do nothing. I complained a bit and was ordered a new battery (which has yet to show up). After finding out that if they did a restore and ran some test and it came back that it was the phone that I would get a refurb. Not what I want. So I went home and did a restore. Let it die all the way and then charged it up over night. The next day, battery life was amazing. Almost 24 hours on a single charge. Good right? Well kinda sorta. Now the phone is doing a random reboot every day or so. At times even twice a day. I'll give it till the end of the weekend and then maybe do another restore. So far, I have mixed feelings about this ICS build.