It was running when I left the house...it was dead when I came back.
The only thing I can imagine is that the power supply finally couldn't take it anymore.
Or, there was a power dip (thunder and lightning...which I don't remember from last night at all) and it couldn't come back to life (with the iPod docked).
Usually, just unplugging the iPod dock and turning the thing to off and back on is enough to get it back, but now, after a whole night of being turned to off, it still can't come back.
Hopefully, my data is all still okay and my mother board isn't fried.