The update program sometimes leaves processes stuck after it finishes. Have you tried a soft reset (hold power switch and volume down until phone reboots) yet? Also, check your apps to see if any are still reinstalling. Until they all finish, it will stay pretty busy, and once they do, you may need another soft reset. You should probably also start each app and make sure all the settings are correct, as sometimes apps with messed up settings can be a problem.