During normal use, my new PowerMac has a very consistent and normal sounding hum. But sometimes I wake up in the middle of the night, and when idle and not sleeping, the PM's sound becomes unconsistent and goes up and down in about 10 second intervals. It will be running, and it will sound like it's about to go to sleep...there will be a slight "click" sound, and then you can hear fans wind down and get quiet...then suddenly it "clicks" again, and the fans wind up and get increasingly louder. It then continues to do this quiet-to loud-to quiet process indefinitely until I begin using it again. It sounds like an interchanging powering down, then powering up, kind of thing. It's hard to explain. It sort of does this (imagine the text below to represent the level of sound): ````````*click*----------..................*click*...........-----------`````````` (not sure if that makes any sense, but it's the best I could do). It kind've sounds like it's trying to sleep, but doesn't quite get there, then powers up again...waits, then tries again. I've got it set for my 56k to disconnect at 55 minutes of idle, and my PM to sleep at 1 hour of inactvity. I've noticed since I've had it that neither one has ever happened on its own. Any help/info/advice is greatly appreciated!