[maquiladora]

Not strictly true, a winter assault would open up, though not completely, a larger number of avenues of approach and make US/SK air sorties more difficult.
Also, if they wanted to just get the attention of the US and blackmail them they would have picked a better time, and not when the US is focused on Iraq.

[MonroeDNA]

What better time to blackmail the US than now?

When we are not about to start a war with someone else?

[streetpreacher]

Also, if they wanted to just get the attention of the US and blackmail them they would have picked a better time, and not when the US is focused on Iraq.

I don't understand your logic here. This is the perfect time for blackmail as the NK understand that we can't offer a ready response to them while we are focusing on a large-scale invasion of Iraq (so they think).