Apple just released a new update 3.1.2 for iPhone and iPod family, the latest update fixes the widely reported issue including iPhone would not wake from sleep, video playback and cellular service, interruption of mobile network services until you restart and los of more. As usual if you relies on unlock never update to stock firmware without pwnage tool and if you are a jailbreaker only wait for GeoHot/Dev team to open their cards.
For your future jailbreak download and save the stock firmware, just click on the iPhone you have. ...