So apple has a bug that has been known since iOS 4.3. I saw this bug in iOS 4.3.1 and it still has not been fixed in iOS 4.3.2. When you launch the camera app going through the specific steps below you will get a message that says: Flash is Disabled The iPhone needs to cool down before you can use the flash.
I know for a fact that my iPhone is not overheating and have even found out a way to replicate this camera roll bug. To see the bug for yourself on iOS 4.3.1 and 4.3.2 follow these steps:
1. Open up the camera app.
2. Switch to the front facing camera.
3. press the camera roll button in the bottom left corner.
4. After viewing the picture press Done.
5. Switch back to the rear camera.
6. You will see a flash symbol with a triangle and exclamation point. Press this and you will see the message pop up on the screen: Flash is Disabled The iPhone needs to cool down before you can use the flash.
This is a really annoying bug but to fix it for now is just to exit out of the camera app and re-open it. Hopefully Apple fixes this in the next iOS firmware update.