The Washington Post issued the report linked below, repeating speculation that it is due to Kim Jong-il's poor health that the delegates to the Worker's Party Congress have been cooling their heels in Pyongyang this past week with no Congress having opened.
I am more inclined to think that this is really about resistance to the installation of Kim Jong-un as hereditary successor. This could be a time of significant court intrigue at the Presidential palace. It is very unlikely to be indicative of anything good going on. If Kim Jong-il does die one could not assume it is necessarily due to natural causes for example.
The delay in opening this Congress is a very worrying development in my judgment.
Still no word from N. Korea about conference delay, but much speculation