blastoff isn't going to happen until a week from today. what needs to be done? nasa will replace an electrical switch box that powers nine critical shuttle systems. to do that, crews need to build scaffolding to test the new equipment and then tear it down. that all has to happen before the launch. and here's a rundown of some other stories we're covering. terrorists secrets taken from the compound where bin laden was killed. the army blows up a levee to save a town in illinois. farmers in missouri are at the mercy of that river. the u.s. relationship with pakistan, after finding bin laden holding out near the capital. plus, grades. what grades? teacher in denver take learning to new levels. mission in afghanistan now that bin laden is dead. ♪ sometimes i feel like... mom! ♪ i know i can count on you