I upgraded my Mac Pro 2006 (full specs in sig) to Snow Leopard last weekend, and since I have noticed that random times throughout the night, or whenever my computer has been in sleep mode, the fans will all kick on in full blast (including the video card, I think). It is similar to when the computer is first turned on, or woke from sleep, except it doesn't turn on...just makes noise for about 5-10 seconds. I haven't been able to really inspect the computer when it does this, as it is completely random, and usually wakes me up. I just look over, and its making loud noises...then stops. My first thought is that this might be a Wake On Demand bug, but I don't have an Airport Base Station, just some D-Link router...but there are other Macs in the house. Any ideas?