[macavenger]

Thanks! Unfortunately, I already thought of that, but I have two problems with that theory:

1) The computer and fridge are on opposite sides of the room, with no contact between the surface on which the computer is sitting (the desk) and the fridge. I rather doubt (although I suppose it is possible) that the floor transfer the vibrations that well.

2) the only part of the computer I can think of that would be affected by vibrations is the mouse, but simply moving the mouse does not wake up the computer. The optical sensor light isn't even on when the computer is asleep.

Is there something I'm missing here? Some other component that might be affected by the vibrations? Or is it something else?