My PowerPC G5 (10.4) went in for repairs a week ago, and had it's Logic Board replaced. When we got it back today, the computer kept going to sleep at random times. Occasionally the fans would whirl like crazy, but not always. I turned it off, and it refused to turn back on for the first three tries, (Automatically shutting off before the start up noise even finished) then on the fourth it turned on and the fans sounded like a jet engine was taking off. The mouse is completely active when it goes to sleep. It goes to sleep when using Photoshop, Firefox (Youtube especially) and MSN. When on youtube it goes to sleep generally 30 seconds to a minute. Otherwise it's random. Using Temperature Moniter I notice on average its CPU temperature ranges from 77-82 C, and when loading a page it's 84-89 C. I did not have this problem before repairs, and the fan generally sounds normal. I've also tried messing with the sleep settings, even turning them completely off or setting it to default. Does anyone know what might be the matter? (It sounds like it may be overheating but I don't know how /I/ could fix that, and it would be a shame to turn around and send it right back in for repairs) Also I'm fairly confident that since they just took it apart that there would be very little, next to no dust in there. Thanks for the help!