Highly Enriched Uranium (HEU) programs don’t pop-up overnight, especially in third-world backwaters like North Korea. Yet North Korea has announced via state-run media that it is capable of the “final stage of uranium enrichment.”
How shocking! There were no clues! There was no way to know this!
Well, not really. All [...]

The title assumes North Korea did test a nuclear device, which I think likely, and not an equivalent amount of TNT, initially thought a possibility in 2006 until radioactive isotopes of krypton and xenon were detected.
There are several reasons for a North Korea to conduct a nuclear test and it’s difficult if not impossible [...]

Update, North Korea’s announcement: Full text of the Korean Central News Agency (KCNA) announcement of the nuclear test, presumably a TV broadcast (via the Independent):
“The Democratic People’s Republic of Korea successfully conducted one more underground nuclear test on May 25 as part of the measures to bolster up its nuclear deterrent for self-defence in [...]

North Korea launched a Taepo Dong 2 (TD-2) missile - probably a space launch vehicle (SLV) - on 05 April 2009. This was a launch of many firsts for Pyongyang, including releasing data about the launch beforehand and some actual video of the event afterwards:

Like the 1998 Taepo Dong 1 (TD-1) launch that [...]

Update: Probably it would have been better to get these answers *before* announcing plans to delist North Korea and remove other trade barriers, as that is what the agreements actually called for:
North Korea did not answer U.S. suspicions of enriching uranium and proliferating technology when it released an inventory of its nuclear plans this [...]

This is almost too good to be true - according to U.S. intelligence sources, the physical records of plutonium processing North Korea gave the U.S. for determining how much had been processed had trace amounts of highly enriched uranium (HEU) on them, and likely not possible transfer from Pakistani equipment supplied by prolific proliferator A.Q. [...]

Victor Cha, in the Chosun Ilbo, discusses the problem - the current lack of a joint plan should Kim Jong-il die and North Korea spirals into chaos:
In what would be the single most important contingency that could impact the South Korean economy and security for decades, there is no agreed upon plan for how [...]

From East-Asia-Intel.com (subscription):
The Dair el Zor raid in Syria on Sept. 6 was not against a nuclear facility but a major arms depot… “Dair el Zor houses a huge underground base where the Syrian army stores the long and medium-range missiles it mostly buys from Iran and North Korea,” the newsletter reported. “The attack [...]

Excerpts from the 26 September Department of State Daily Press Briefing on sanctions being placed on a state owned North Korean company for missile technology transfer (not Syria), and possible effects on the Six-Party Talks. Deputy Spokesman Tom Casey is responding to questions:
QUESTION: Yeah, North Korea. I know that you touched on this yesterday, but [...]

Excerpts from the 25 September Department of State Daily Press Briefing on the election of Prime Minister Yasuo Fukuda and new sanctions on North Korean company producing missiles. Deputy Spokesman Tom Casey is responding to questions:
QUESTION: A new Japanese cabinet was formed today under the LDP leader Yasuo Fukuda and what are U.S. expectations of [...]