iMac G5 Rev B, 2GB RAM, 10.5.7 It suddenly developed the following maladies overnight: 1) It won't sleep. When you select sleep from the menu, the screen darkens, the fans continue for about a minute, then the fans rev up to max speed. It never displays the pulsing white light, and the only option is to hold the power button down to shut it off. 2) It won't shutdown properly. It does shutdown, but rather than take ~10-15 seconds it now takes about a minute before the blissful silence of halted fans. 3) It takes much longer to boot than I remember, and the blue horizontal progress bar doesn't show up. It goes instantly from empty blue screen to login window plus starry background.