I have an Imac G5 that I am unable to adjust brightness on. I have gone into system and than display and have adjusted the brightness but as soon as I let go it reverts back. There is also a transparent icon on the screen that appears to be for brightness that when I adjust the bar at the bottom turns green. This transparent icon has been there since yesterday and I am not sure how to get rid of it. Just to give you a heads up, the user spilled water on the keyboard yesterday and the keyboard was unusable. It has since dried and is working again. I do not have a spare keyboard to replace it.