Apple Computer cried "uncle" Tuesday, and promised it would replace defective iPod nano screens that have cracked. It won't, however, deal with users who claim that the device's case scratches easily. According to reports in the Wall Street Journal, a "vendor quality problem" caused cracking on a small number of iPod nano screens, said Philip Schiller, Apple's senior vice president of worldwide product marketing. The problem affected "less than one-tenth of 1%" of the nanos shipped, Schiller said. Users had posted messages on Apple's own support forums as well as other sites -- including financial services consultant Matthew Peterson's flawedmusicplayer.com...