I've just had something really annoying happen. I noticed yesterday that my 23" ACD, which I use as a secondary monitor, power light was going on and off even though the monitor appeared to be working fine. When I put the computer to sleep the monitor stayed on (I could see the backlight lighting up the screen even though it was black). Now the power light stays off, the monitor works, but I can't adjust the brightness and the power button doesn't work. When I go the System Preferences and Displays there is no brightness slider available for the 23". I have tried unplugging it, rebooting the computer etc, and even booting up in my backup of Leopard (I usually use Snow Leopard) but it doesn't change anything. Anyone else had this issue? I did have a power cut the other day, but I don't know how that could have affected it.