Well the story is not good as far as I can tell. My source had a few beers with oune of the engineering team, and its a structural problem with a section of the wing box area that is part of the new wing desgn that allows all the flex in the new wing.
Whatever the rework is..... sounds huge to me!
So as somone else posted above..... the butt covering and "fibbing" about the delays sort of says it all really.
Things are very tight lipped in Everett!