Apple just released iPhone OS 3.1.2 software, the main fixed iPhone can not wake up the situation when it in the lock screen, there may be some users have already encountered such problems, and often through the cold start to be resolved.
This update contains bug fixes and improvements, including the following:
(1) Resolves sporadic issue that may cause iPhone to not wake from sleep
(2) Resolves intermittent issue that may interrupt cellular network sevices until restart
(3) Fixes bug that could cause occasional crash during video streaming