I have been wondering what had been causing the fans to ramp up to 6000 RPM on my Macbook Alu for a while now, and decided to spend a while yesterday looking into the cause. It seems to be caused by the Fliqlo screensaver on Snow Leopard. I checked Console and found that it was crashing on startup and then restarting a few times before it would run correctly. I don't know why it would cause the fans to ramp up to the maximum on this computer, but there is a definite correlation between the times the fan comes on and the times the screensaver is active. The same problem (although without the fans) has occured on my MBP 13", so it is not restricted to the unibody Macbook. Unfortunately I have since cleared my logs on both computers and uninstalled the screensaver for the time being so I can't post a copy of the error. I take it this is occuring for everyone?