I have a PB Onyx 667. It is exhibiting some very strange behavior. First off, it doesn't startup. It chimes just fine, but that's it, no screen boot - it just sits, doesn't turn off, but sits. Furthermore, if I force restart, which it will do, it does not respond to key commands, such as flashing the PRAM. I noticed the fan at the rear of the case is not spinning up. Another symptoms is that about 1 in 20ish startups the it boots to the grey screen with the apple in the middle, and hangs there. The screen will flicker, and then go out. If I wiggle the screen (it has a broken hinge) the screen will flicker in and out. Thius would indicate a damage screen connection, but the plot thickens, the VGA out does not function either, but when the computer magically decides to boot to the grey apple screen, the external monitor works as well, indicating the problem is further upstream. Now here is the kicker: I decided to put the PB into the freezer for a few minutes on a whim. Sure enough it booted right up into the OS, and functioned perfectly for a minute or two until it regained room temperature. Thus I concluded it is some kind of heat problem. It is not actually overheating, but I think it believes it is (smart little guy). Does anyone know anything about the thermostatic mechanism? Any help would be greatly appreciated!!