Several users have reported an issue in which the iPhone 3G's screen suddenly goes black, as if the sleep/wake button has been pressed. When this problem manifests, users generally need to press the sleep/wake button twice, effectively putting the device into a locked state then unlocking it.
In some cases, this issue is caused by obstruction of the proximity sensor, generally caused by a case or errant hand. Many users experiencing the issue, however, have neither of these interference factors.
Sample posts from this Apple Discussions thread include:
- "Mine has exhibited the exact same behavior. I have reset a countless amount of times. And performed a restore to get build 7 also. Overall, it doesn't impact my use of the phone. So I'm hoping it gets resolved with the next firmware build."
- "I just bought iphone 3G for few days, and it's having the same problem as you do. The screen keeps going blank even when there's no case block the sensor and even with built-in apple apps such as setting."
Workaround This issue can generally be resolved by turning off the Password Lock (PIN) function in Settings.