Not to be raise threads from the dead, but I was curious if the SIM replacement resolved the issue. One of my users is experiencing this problem with his 8310. It's not the battery charge level like everyone is so anxious to point out. The phone is running the latest OS and has otherwise worked fine. I was going to give him a new BlackBerry when he's back from traveling, but if replacing the SIM is the solution I'd obviously like to do that instead.