[onewhippedpuppy]

I would try pulling every dead outlet or switch and checking for power, starting with the one closest to a breaker box. Figure out where you have power coming in, but not power going out. Or power going out of a box, but not making it to the next box. If you have a dead wire you can verify point A to B by disconnecting both, jumping one side, and using a continuity test on the other to insure that the wires run between these boxes. If the electrician was any good the routing should be logical.

I bet (hope?) that you'll find an obvious smoking gun when you start pulling outlets and switches.