Thanks for clearing that up - it's always been bothering what it could possibly be (that and the "how on earth did he figure that out in the first place?")

The cold would shrink the motherboard to re-connect the contacts; it might have been fixed by doing the old Xbox/nvidia trick of putting it in the oven (which would soften the solder, causing it to shift and re-connect). With the Xbox, you could apparently even just wrap it in a towel and let its own heat do the trick.