It’s amazing how bloody clueless both Bush and His Evil Minions™ and the press covering this don’t get it, as typified by the hed, “U.S. Bewildered Over N. Korea Nuclear Defiance.”
It’s very simple. While the folks in North Korea are not particularly trustworthy, there has been a consistent pattern where they have taken steps they have agreed to, and the US has refused to make the steps that it has agreed to.
You could pull the DPRK off the list of “terrorist sponsoring states” in 15 minutes, and you could put them back in 15 minutes, but the brainless trust headed by Cheney and Rice won’t do anything ever, because keeping our side of the bargain is to their minds capitulation.
The North Koreans are restarting their Yongbyon nuclear power plant because they have absolutely no faith in the word of the United States to keep the deal.