Dominic Gates of the Seattle Times wrote an in depth article giving more details on Boeing's decision to temporarily halt 787 part deliveries into Everett.
Among the details is that Dominic reveals is that some major suppliers are shipping sections that have the inside that are only 60% complete. This is leading to travelled work being done at Everett which Boeing had experienced early in the program. This time the part shortages are related to changes in the design of some parts in order to save weight. Some suppliers are still implementing the engineering changes to the parts.
Dominic's article has a lot of great details about the situation:
Dominic Gates: Boeing suspends delivery of new 787 sections to Everett