What did I do wrong when replacing a switched power receptacle?
You forgot to break the tab on the hot side off the receptacle in the half-switched spot, shorting out the switch and making both halves of the receptacle always on.  The easy fix for this is to turn the power off at the breaker, pull out the supposed-to-be-half-switched receptacle, break the tab on the hot (brass screws) side off, button things back up, and turn the power back on.