Getting back to my comment about a nuke going off here… This is where it would probably come from:
http://www.cnn.com/2007/US/08/10/pakistan.nuclear/index.html
Musharraf dies in a bloody coup, rebels sell off a nuke to a terror cell for a quick buck, nuke “disappears” until it goes boom in NYC.
And unlike the nuclear “threat” from Russia, where the obvious mutal destruction has kept the peace for years, in this case you’d have no one to threaten with blowing off the map. By the time the nuke goes off power will probably have shifted away from the rebel coup and Pakistan would be an ally again.
Nukes are great when they’re kept between superpowers. The fact that both sides know using them would result in total annihilation keeps either side from using them. That’s why I will never be too worried about a Russian nuke threat. The problem is that now nukes aren’t only in the hands of two superpowers.