fading display on iPhone 3GS The display on my iPhone 3GS keeps randomly fading in colour. Sometimes unlocking the screen is normal, sometimes faded its still visible but much paler than normal. 

If I lock and unlock the screen several times it usually clears it but then after a period of non use its back to pale when I unlock, or not, as the case may be

Can't find any info anywhere relating to anything like this. has anyone any ideas please?
Have you checked that Auto Brightness is on?

Go to settings>brightness you then have a slider to change the brigntness of the screen and the auto brightness switch.

If this is on, it uses the light sensor by the camera to adjust the brightness with the ambiant light.