Having a strange issue that I searched for, but couldn't find anything like my experience. Recently, after about 5 minutes of use (not sitting idle), my MacBook's screen will go very dim. I hit the buttons on the keyboard to take the brightness all the way up, but it doesn't get much brighter and there's only one thing that I can do to make the screen go brighter: I go into System Preferences and click Display. The second I click that, the brightness returns without me doing anything in the Display section, so after Display comes up, I just close it out and the screen brightness is fine for a while. It seems to do this after the lid has been closed for a while and then starts dimming again after opening the lid and using it for about 5 minutes. Any thoughts on this? Is there a way to fix the auto-dim mode without disabling it? MacBook (white) is running Leopard 10.5.8 with all the latest updates.