Just for the record: I don't have any answers. I don't think Josh Marshall makes a compelling case that Bush 43 screwed the pooch, but I don't know that Bush 43 is 100% right either.
What I will say is that I think it's way to early to start assigning blame; North Korea is clearly taking advantage of the South Korean interregnum, world preoccupation with Iraq, and a general need for Kim Jong Il to be the center of attention at any party. Maybe the PRK feels disrespected by the Bush administation, but that doesn't excuse the six years of broken promises during the Clinton era. If anything, the sabre rattling this time has been less intense (a preemptive strike on PRK nuclear facilities isn't on the table in 2002, but it certainly was in 1994, perhaps due to Clinton's fascination with Blip Warz as a foreign policy tool). Unlike Marshall, I'm pretty sure Bush isn't bluffing and the U.S. and South Korea can successfully resist an invasion by the North.
I just realized that the above is basically a bunch of unrelated sentences strung together, rather than a paragraph. Sue me.