Apple has just released iPhone OS 3.1.2 for the iPhone and also the iPod Touch. The Update addresses some network issues, sleep/wake trouble as well as video streaming troubles. You can get it via iTunes now.
This update contains bug fixes and improvements, including the following:
– Resolves sporadic issue that may cause iPhone to not wake from sleep
– Resolves intermittent issue that may interrupt cellular network services until restart
– Fixes bug that could cause occasional crash during video streaming
Of course if you have a Jailbroken iPhone you will want to hold off a bit to be safe.