I have just seen this strange entry in my system log :-
Jul 18 10:32:56 Ian-Computer kernel[0]: AppleSMU::setLEDdimmOffset(1 hrs offset from GMT) to rise at 07 hrs GMT and set at 19 hrs GMT to 24 pct LED brightness with 35 min transitions.
Could this mean that 10.4.2 contains some code to dim the LED on the from of my iMac G5 between the hours of 7pm and 7am? I know the latest iMacs have an ambient light sensor but the early models (like mine) did not. I know they did talk about a firmware update to fix this, but maybe it has been built into the OS.
I will have a test tonight and see if the LED is dimmer.
IAN