I had to go and brag about it

So what happens when you go and say that something will be finished on a certain day?  Murphy shows his ugly head.
Damn you, Murphy.
See, everything was ready.  I had bought an extension hose for the shop vac, and onsrud cutters for the router. I had even done testing!  Apparently, I hadn't done enough.  Here's what happened:
I got the new motor wired up to one of my cables, poped it on the y axis (it had a longer drive shaft than my other motors, so it fit better there), connected everything, and loaded up the config wizard to make sure my settings were right.  X and y axises still worked fine (so the new motor was good), but when I tried to test the z axis, nothing happened.  I called someone over to listen to the motor while I tried to drive it, and apparently it would make a faint humming noise, but that was it.  I disconnected it from the z axis lead screw, and it still didn't move.  Out came the multi-meter.  The cable was good.  The port on the electronics box was good.  I tested the motor on a different stepper driver board and it worked just fine, so it wasn't the motor.  This leaves (as far as I know) only one thing that could be failing to work: the z axis stepper driver board.
Some good news:  The guy who built the electronics is going to be here soon, he should be able to accurately diagnose the problem.  With any luck, it's something silly I didn't know about, and he'll fix it.  Also, I have an extra driver board that only needs very minor repairs to be fully functional, so even if the current z axis board is busted, we've got a replacement; no waiting for shipping.
Wish me luck!