Pulled the front cover back off. Everything looked okay, and when I plugged it back in and pushed down on the latch switch, it started to spin up...but there was a "clicking relay" sound coming from the motor and it wasn't spinning up smoothly. Finally, after a few seconds of this, it stopped again.
Therefore I must've put something back together wrong, or something. It's taking too much power to spin up, which is causing an overheat or overload condition, and the motor switch is helpfully doing its job and keeping the motor from frying itself.
Anyway, tomorrow's another day, I guess. Anyone got a time machine, so I can take a couple days off after my weekend without getting in trouble at work?