Since the missle tests on July 4th, North Korea has allegedly launched "Distributed Denial-Of-Service" or Attacks over the Internet on South Korean and U.S. governmental websites. South Korea's National Intelligence Service (NIS) have blamed North Korea, more specifically:
"It told lawmakers in a closed-door briefing Friday that a North Korean military research centre called 'Number 110' seems to have orchestrated the attacks, according to Yonhap news agency" (South Korea downgrades cyber attack alert AFP).
"Ruling out any direct talks with North Korea on nuclear disarmament negotiations, the US today said Pyongyang can only be engaged multilaterally through the six-party mechanism" ("US rules out any direct talks with North Korea" : Business Standard).
For, you see, I think North Korea does not very much like these six-party talks as it's basically like a situation when say I'm just interested in what just one particular person has to say, but there are these other people who have something to say to you as well (잔소리/Scolding from so many parties). On the other hand, from China's perspective, each round of its successful hosting shows that China has matured as a responsible power that understands the dangers of North Korean nuclear weapons proliferation and just hosting it shows off the country's power as it shows how China has brought North Korea to the negotiating table. It's mere hosting is seen as a success for China.
For the United States, it's a way to deflect responsibility or rather, a way to ensure that the United States is not the sole party responsible to denuclearize North Korea. Japan's foreign policy with respect to North Korea is held hostage to its very loud and powerful ultraconservative wing of the LDP as the forum has been the main and only one for Japan to express discontent at North Korea for not talking more about hostages (Even as recently, a group of South Korean fisherman have been taken into North Korean custody and a South Korean worker at Gaeseong still remains in North Korean custody). Yet, South Korea too, shows how it's a responsible party by placing sanctions on North Korea at least on a nominal basis and even having recently joined the PSI (Proliferation Security Initiative).
Then, only after having to hear all these things that these people (countries) have to say about your behavior and only then, can you finally get to hear what the United States (the only person you're interested in) has to say.
So, you can see the reasoning behind why:
"North Korea has said the purpose of the six-nation talks was to 'disarm and incapacitate' it"("North Korea Asserts New Willingness to Talk" : New York Times).
On a personal note, I'm surprised that North Korea hasn't done more to garner more U.S. attention and lets hope that this august will be a quiet august.